Reducing Risk and Managing Your Custom Fields

Have you ever wondered how to properly name keys of WordPress custom fields? Does it make any difference? Should you care? What are the potential risks?

Recently I wrote a tutorial about filtering WordPress admin views. In the code, I named custom fields key like kg_order_items. You could ask why? Why not name it just items? Well… read below!

If you try to google for naming custom fields there is not so much information about it. Even the Codex entry tells nothing about naming the field keys in a proper way. I found only one resource at ACF forums that contains proper information.

If there is no problem, what is the fuss about? You could ask.

The days when WordPress was a simple CMS supporting small blog websites with only posts and pages are gone. Today even the smallest website uses a plethora of plugins and complex themes. And all of them bring new custom fields into the game.

The situation gets even worse if you use any of the fancy “premium” themes. Unfortunately, many of these are not well written and combine 1001 functions in one. Final result? Slow, not performant, and tangled site which looks nice only on demo content and stock images. And they add a lot of custom fields too.

Danger!

WordPress wp_postmeta table is very simple. It is a key-value pair attached to particular post_id. It means that all custom fields keys share a common namespace. That is especially true for the particular ID of the post.

First example
a) Imagine that your post has a “learn more” link. After you click the link it redirects you to a particular URL. The address is provided in a custom field. Let’s name the field key as redirect_to.

b) Now imagine that you install a plugin called for example “Redirect me, Honey”. The plugin is very, very simple. When the user enters the page it immediately redirects the user based on custom field setting attached to a post. Oh… and its field key is named redirect_to as well.

Result? After you activate the plugin, all of your posts with “learn more” button are redirecting users out of your website. And the reason why is not obvious at the first sight. It may even be unnoticed for quite a while.

This scenario is, of course, made up but the dangers are real. With thousands of plugins and thousands of themes available it’s just a matter of time to encounter such name collision.

Second example
WordPress can store multiple values for the same key name and post ID. (Unless you provide special parameter called $unique).

It means that if you save your data 5 times under the key location you will receive an array consisting of 5 elements when calling get_post_meta().

Let’s assume that you have a post about the cities you have visited. You have been to 5 cities and those locations are shown on the embedded map in the post. Simple, right?

Attention! Not useful code ahead. ;) !

//NY
add_post_meta($post_id, 'location', '40.7127753, 73.989308'); 

//LA
add_post_meta($post_id, 'location', '34.0522342, -118.2436849');

//Paris
add_post_meta($post_id, 'location', '48.856614, 2.3522219000000177'); 

//Vienna
add_post_meta($post_id, 'location', '48.2081743, 16.37381890000006'); 

//Rome
add_post_meta($post_id, 'location', '41.90278349999999, 12.496365500000024');

//Lets check what we have here
var_dump(get_post_meta($post_id, 'location');

array (size=5)
0 => string '40.7127753, 73.989308' (length=21)
1 => string '34.0522342, -118.2436849' (length=24)
2 => string '48.856614, 2.3522219000000177' (length=29)
3 => string '48.2081743,16.37381890000006' (length=28)
4 => string '41.90278349999999,12.496365500000024' (length=36)

What if after a while you use a new theme or plugin. It has a feature which can set the position of a post on a front page. You can pick between slider, sidebar or featured posts etc. This scenario may end up like this:

array (size=6)
 0 => string ‘40.7127753, 73.989308’ (length=21)
 1 => string ‘34.0522342, -118.2436849’ (length=24)
 2 => string ‘48.856614, 2.3522219000000177’ (length=29)
 3 => string ‘48.2081743,16.37381890000006’ (length=28)
 4 => string ‘41.90278349999999,12.496365500000024’ (length=36)
 5 => string ‘left_sidebar’ (length=12) // Yeah, right…

Or even worse:

array (size=5)
  0 => string 'left_sidebar' (length=12)
  1 => string 'left_sidebar' (length=12)
  2 => string 'left_sidebar' (length=12)
  3 => string 'left_sidebar' (length=12)
  4 => string 'left_sidebar' (length=12)

Your pretty little map is broken now! And you lost all of your entered data. Not funny right?

Solution

You can never protect your custom fields data from being overwritten or deleted. This is how WordPress works and why it is so flexible. You can reduce that risk though.

How?
By avoiding common names and namespacing all your custom fields keys.

My proposed convention is:

• cpt-name_field-name
  like books_author instead of author, order_items instead of items(solution for most lazy ones :) ).
• purpose_field-name
  like front_page_location instead of location, visited_cities_locationsinstead of location.
• prefix_(cpt-name/purpose)_field-name
  like kg_books_author, kg_visited_cities_locations (for the most strict ones).

That is not all. Additionally, you should always take care of optional parameters of built-in WordPress functions:

• add_post_meta() has $unique to not add the custom field if it already exists.
• get_post_meta() uses $single to retrieve only one record (if you expect only one record).
• update_post_meta() and delete_post_meta() leverage $previous_value to ensure that you update/delete the key you want.

Those parameters are helping in writing better, cleaner and more predictable code.

And that is not all. Use well tested, well written and extendable plugins like Pods Framework or Advanced Custom Fields. These will help manage your custom fields. They are great when it comes to managing the tangled world of your custom data.

Summary

In the ideal world, we should always be aware of what you are adding to the system. We should know what your plugins, themes, and custom functions are doing. That is unfortunately not always possible.

Therefore we should pay attention to the code we produce and tighten up all those loose ends.

That is all folks! I hope you liked it and have a great day!

This post was originally published on my private blog where I write about WordPress and development in general. You can follow me on Twitter or check my private photography project. Oh and you can hire me too
Wanna some more links? No? Okay ;(

The Tangled World of Custom Data in WordPress was originally published in freeCodeCamp on Medium, where people are continuing the conversation by highlighting and responding to this story.

Five hundred open source projects in need of design help

Backstory

You’re a designer. You would like to get involved in open source but don’t know where to begin. You don’t want to work on any open source project. You want to make an impact. But how can you find open source projects that are looking for design help and are being used by many people?

I’ve been asking myself this question for at least a few months. I haven’t been able to find the answer on the web. So I decided to treat it as a design problem.

For more than a year, I explored my answers to the question “What would you like to do if money were no object?” “Building free software” was one of my answers.

I did my research. Most open source projects are on GitHub. GitHub has a feature where users can star projects. This is how GitHub describes stars:

You can star repositories to keep track of projects you find interesting and discover similar projects in your news feed.

Starring a repository makes it easy to find again later. […]

Starring a repository also shows appreciation to the repository maintainer for their work.

In the absence of better alternatives, I allowed myself to assume that the number of stars could serve to measure the impact of a project.

Things to do in projects are called “issues” on GitHub. GitHub has a search engine. Is it possible to do a GitHub search for current issues labeled “ux”, “ui” or “design” and sort them according to the number of stars awarded to the projects?

No.

Hmm.

I learned what I needed to learn and wrote a program that builds such a list. At the time of this writing, it returns 17,742 issues. 17,742 things to do in 2,942 projects. It took two hours to extract all this data from GitHub. And these are just the things from the last 12 months. It’s an excessive amount of data.

What can be done with all this data? A lot. The first thing I’m doing is making the following list of 500 open source projects in need of help from designers. I hope that this is an inspiration for you. It helped me and I believe that it will help you too.

1. freeCodeCamp/freeCodeCamp・291470 stars

2. atom/atom・42019 stars

3. Microsoft/vscode・39428 stars

4. jekyll/jekyll・32036 stars

5. getlantern/lantern・30073 stars

6. zurb/foundation-sites・26701 stars

7. neovim/neovim・25132 stars

8. TryGhost/Ghost・24453 stars

9. nylas/nylas-mail・23737 stars

10. ant-design/ant-design・20182 stars

11. Leaflet/Leaflet・20065 stars

12. apache/incubator-superset・16920 stars

13. storybooks/storybook・16143 stars

14. npm/npm・14633 stars

15. facebook/jest・13737 stars

16. angular-ui/ui-router・13671 stars

17. ipython/ipython・12177 stars

18. angular/material2・12073 stars

19. NativeScript/NativeScript・11807 stars

20. diaspora/diaspora・11493 stars

21. keystonejs/keystone・11433 stars

22. tootsuite/mastodon・11413 stars

23. source-foundry/Hack・10407 stars

24. LightTable/LightTable・9930 stars

25. JuliaLang/julia・9577 stars

26. Automattic/wp-calypso・9463 stars

27. fabric/fabric・9298 stars

28. pockethub/PocketHub・9087 stars

29. chmln/flatpickr・9055 stars

30. spree/spree・8870 stars

31. WhisperSystems/Signal-Android・8475 stars

32. elastic/logstash・8302 stars

33. OpenEmu/OpenEmu・8187 stars

34. docker/kitematic・8057 stars

35. metabase/metabase・7605 stars

36. FineUploader/fine-uploader・7346 stars

37. Wox-launcher/Wox・7329 stars

38. CachetHQ/Cachet・7300 stars

39. mailpile/Mailpile・7141 stars

40. mozilla/metrics-graphics・6759 stars

41. ether/etherpad-lite・6621 stars

42. apex/apex・6386 stars

43. travis-ci/travis-ci・6263 stars

44. ory/editor・6232 stars

45. brave/browser-laptop・6227 stars

46. SFTtech/openage・6213 stars

47. telegramdesktop/tdesktop・6106 stars

48. ianstormtaylor/slate・6051 stars

49. insidegui/WWDC・6036 stars

50. reactioncommerce/reaction・6009 stars

51. joemccann/dillinger・5716 stars

52. keeweb/keeweb・5687 stars

53. owncloud/core・5656 stars

54. zulip/zulip・5582 stars

55. gravitational/teleport・5431 stars

56. the-control-group/voyager・4990 stars

57. MonoGame/MonoGame・4724 stars

58. OpenRA/OpenRA・4657 stars

59. ant-design/ant-design-pro・4527 stars

60. topcoat/topcoat・4276 stars

61. icsharpcode/ILSpy・4105 stars

62. Strider-CD/strider・4053 stars

63. spinnaker/spinnaker・3940 stars

64. rsms/inter・3917 stars

65. rtfd/readthedocs.org・3873 stars

66. prose/prose・3869 stars

67. apex/up・3835 stars

68. HospitalRun/hospitalrun-frontend・3772 stars

69. Sylius/Sylius・3723 stars

70. mattgodbolt/compiler-explorer・3584 stars

71. netlify/netlify-cms・3582 stars

72. askmike/gekko・3575 stars

73. scylladb/scylla・3539 stars

74. malcommac/SwiftDate・3435 stars

75. jaegertracing/jaeger・3391 stars

76. koreader/koreader・3382 stars

77. flarum/core・3380 stars

78. apache/couchdb・3338 stars

79. nextcloud/server・3221 stars

80. wallabag/wallabag・3172 stars

81. vmware/harbor・3146 stars

82. HearthSim/Hearthstone-Deck-Tracker・3133 stars

83. hashicorp/nomad・3040 stars

84. mawww/kakoune・2995 stars

85. transloadit/uppy・2995 stars

86. twitter/heron・2990 stars

87. jupyter/jupyter・2941 stars

88. googlearchive/chromedeveditor・2901 stars

89. eventbrite/britecharts・2890 stars

90. postmanlabs/postman-app-support・2854 stars

91. ricochet-im/ricochet・2812 stars

92. HubPress/hubpress.io・2773 stars

93. benvanik/xenia・2753 stars

94. NVIDIA/DIGITS・2712 stars

95. phpmyadmin/phpmyadmin・2708 stars

96. martanne/vis・2700 stars

97. pyrocms/pyrocms・2672 stars

98. sitespeedio/sitespeed.io・2659 stars

99. lektor/lektor・2567 stars

100. TykTechnologies/tyk・2558 stars

101. mozilla-services/react-jsonschema-form・2504 stars

102. lesspass/lesspass・2481 stars

103. kangax/compat-table・2443 stars

104. statsmodels/statsmodels・2424 stars

105. Microsoft/sqlopsstudio・2402 stars

106. gitextensions/gitextensions・2374 stars

107. redox-os/tfs・2372 stars

108. gephi/gephi・2353 stars

109. owncloud/android・2335 stars

110. duplicati/duplicati・2322 stars

111. freedomofpress/securedrop・2210 stars

112. MovingBlocks/Terasology・2203 stars

113. rundeck/rundeck・2189 stars

114. thoughtbot/shoulda-matchers・2155 stars

115. wordpress-mobile/WordPress-iOS・2104 stars

116. aseprite/aseprite・2081 stars

117. nteract/nteract・2059 stars

118. iron-meteor/iron-router・2057 stars

119. cssmagic/blog・2023 stars

120. tomahawk-player/tomahawk・2004 stars

121. wireapp/wire-android・1976 stars

122. EFForg/https-everywhere・1960 stars

123. bigbluebutton/bigbluebutton・1944 stars

124. opentoonz/opentoonz・1928 stars

125. prikhi/pencil・1919 stars

126. ktorio/ktor・1913 stars

127. iron-io/functions・1861 stars

128. getguesstimate/guesstimate-app・1854 stars

129. howtographql/howtographql・1852 stars

130. CMB2/CMB2・1838 stars

131. Netflix/security_monkey・1833 stars

132. OpenZeppelin/zeppelin-solidity・1812 stars

133. punkave/apostrophe・1807 stars

134. mumble-voip/mumble・1794 stars

135. OpenGrok/OpenGrok・1764 stars

136. fnproject/fn・1747 stars

137. ckan/ckan・1744 stars

138. ampache/ampache・1734 stars

139. fontforge/fontforge・1714 stars

140. trailsjs/trails・1693 stars

141. CartoDB/cartodb・1647 stars

142. alexrj/Slic3r・1643 stars

143. asciidoctor/asciidoctor・1641 stars

144. onyx-platform/onyx・1633 stars

145. solidusio/solidus・1608 stars

146. SUSE/Portus・1606 stars

147. rubygems/rubygems.org・1600 stars

148. divmain/GitSavvy・1597 stars

149. atom/teletype・1587 stars

150. wordpress-mobile/WordPress-Android・1585 stars

151. goldendict/goldendict・1574 stars

152. LMMS/lmms・1572 stars

153. frontendbr/forum・1568 stars

154. verdaccio/verdaccio・1566 stars

155. Radarr/Radarr・1565 stars

156. canjs/canjs・1547 stars

157. status-im/status-react・1546 stars

158. snipe/snipe-it・1525 stars

159. git/git-scm.com・1522 stars

160. montagejs/montage・1519 stars

161. sagalbot/vue-select・1508 stars

162. SSilence/selfoss・1493 stars

163. NixOS/nix・1488 stars

164. SpiderOak/Encryptr・1460 stars

165. vector-im/riot-web・1432 stars

166. swimlane/ngx-charts・1432 stars

167. kimchi-project/kimchi・1410 stars

168. django-admin-bootstrapped/django-admin-bootstrapped・1405 stars

169. seven332/EhViewer・1401 stars

170. Teradata/covalent・1376 stars

171. WordPress/gutenberg・1347 stars

172. jnunemaker/flipper・1322 stars

173. duckduckgo/duckduckgo・1316 stars

174. pypa/warehouse・1285 stars

175. wesnoth/wesnoth・1264 stars

176. bitovi/jquerypp・1256 stars

177. 720kb/ndm・1238 stars

178. ASKBOT/askbot-devel・1231 stars

179. nyaadevs/nyaa・1224 stars

180. mustache/mustache.github.com・1220 stars

181. icefox/git-achievements・1213 stars

182. corda/corda・1207 stars

183. donejs/donejs・1202 stars

184. blockstack/blockstack・1188 stars

185. firebug/firebug・1169 stars

186. nunit/nunit・1150 stars

187. osTicket/osTicket・1141 stars

188. mozilla/thimble.mozilla.org・1129 stars

189. isaacs/github・1118 stars

190. GSA/data.gov・1114 stars

191. Elgg/Elgg・1097 stars

192. Automattic/simplenote-android・1045 stars

193. Schmavery/facebook-chat-api・1034 stars

194. ankidroid/Anki-Android・1028 stars

195. bpmn-io/bpmn-js・1028 stars

196. boostorg/beast・1016 stars

197. jxtech/wechatpy・1012 stars

198. 24pullrequests/24pullrequests・1003 stars

199. composer/packagist・1002 stars

200. iRareMedia/iCloudDocumentSync・997 stars

201. justwatchcom/gopass・987 stars

202. smartstoreag/SmartStoreNET・974 stars

203. purpleidea/mgmt・970 stars

204. dotnet/corefxlab・965 stars

205. translate/pootle・929 stars

206. modoboa/modoboa・910 stars

207. devsnd/cherrymusic・909 stars

208. craftcms/cms・896 stars

209. lightningnetwork/lnd・891 stars

210. fritzing/fritzing-app・889 stars

211. pantsbuild/pants・883 stars

212. stampery/mongoaudit・883 stars

213. EFForg/privacybadger・881 stars

214. jfurrow/flood・872 stars

215. mypaint/mypaint・864 stars

216. mixxxdj/mixxx・858 stars

217. thredded/thredded・844 stars

218. Yoast/wordpress-seo・816 stars

219. trailofbits/manticore・812 stars

220. atom/autocomplete-plus・810 stars

221. blockstack/blockstack-browser・809 stars

222. mirage/irmin・806 stars

223. 4pr0n/ripme・779 stars

224. frappe/frappe・776 stars

225. boostorg/compute・772 stars

226. yeoman/yeoman.github.io・762 stars

227. guyzmo/git-repo・741 stars

228. securitywithoutborders/hardentools・739 stars

229. python/pythondotorg・737 stars

230. allegro/ralph・737 stars

231. material-foundation/material-remixer-android・734 stars

232. ThemeFuse/Unyson・730 stars

233. brave/browser-ios・730 stars

234. duckduckgo/zeroclickinfo-goodies・725 stars

235. akira/exq・712 stars

236. patternfly/patternfly・711 stars

237. JabRef/jabref・704 stars

238. securitytxt/security-txt・702 stars

239. mozilla-mobile/focus-ios・697 stars

240. owtf/owtf・688 stars

241. eslint/espree・687 stars

242. potree/potree・681 stars

243. mavlink/qgroundcontrol・672 stars

244. insidegui/PodcastMenu・667 stars

245. funretro/distributed・655 stars

246. projecthamster/hamster・654 stars

247. pods-framework/pods・653 stars

248. firasdib/Regex101・652 stars

249. FreshRSS/FreshRSS・649 stars

250. opentx/opentx・641 stars

251. LLK/scratch-blocks・640 stars

252. solvespace/solvespace・640 stars

253. HTBox/allReady・629 stars

254. factor/factor・628 stars

255. wavebox/waveboxapp・619 stars

256. nodejs/nodejs.org・612 stars

257. NativeScript/nativescript-cli・605 stars

258. glowing-bear/glowing-bear・605 stars

259. erengy/taiga・595 stars

260. bitovi/funcunit・585 stars

261. sulu/sulu-standard・585 stars

262. webrecorder/webrecorder・583 stars

263. hsz/idea-gitignore・582 stars

264. mulesoft/api-console・579 stars

265. eclipse/smarthome・579 stars

266. emberjs/website・576 stars

267. emoncms/emoncms・572 stars

268. vickychijwani/quill・563 stars

269. ManageIQ/manageiq・562 stars

270. simonmichael/hledger・554 stars

271. wroscoe/donkey・537 stars

272. rwengine/openrw・528 stars

273. alephdata/aleph・518 stars

274. hootsuite/atlantis・513 stars

275. nextcloud/android・511 stars

276. DynamoDS/Dynamo・511 stars

277. consul/consul・509 stars

278. GoldenCheetah/GoldenCheetah・503 stars

279. flosell/lambdacd・503 stars

280. friendica/friendica・500 stars

281. noflo/noflo-ui・498 stars

282. KeitIG/museeks・497 stars

283. mozilla-mobile/focus-android・489 stars

284. exercism/cli・488 stars

285. scout-app/scout-app・487 stars

286. coreinfrastructure/best-practices-badge・486 stars

287. h2non/gentleman・478 stars

288. owncloud/ios・473 stars

289. hyperledger/composer・472 stars

290. vifm/vifm・470 stars

291. prusa3d/Slic3r・467 stars

292. agrafix/Spock・463 stars

293. vector-im/riot-android・462 stars

294. log2timeline/plaso・457 stars

295. GhostText/GhostText・446 stars

296. ushahidi/platform・443 stars

297. EFForg/privacybadgerfirefox-legacy・442 stars

298. influxdata/chronograf・435 stars

299. istresearch/scrapy-cluster・433 stars

300. tgstation/tgstation・432 stars

301. quodlibet/quodlibet・429 stars

302. wallabyjs/public・422 stars

303. colobot/colobot・421 stars

304. chronotope/chrono・418 stars

305. ParabolInc/action・417 stars

306. atom/tree-view・415 stars

307. spack/spack・413 stars

308. HabitRPG/habitica-android・410 stars

309. osresearch/heads・410 stars

310. gdg-x/hoverboard・404 stars

311. fossasia/open-event-webapp・404 stars

312. owncloud/apps・402 stars

313. julianguyen/ifme・402 stars

314. google/blockly-android・402 stars

315. hashview/hashview・401 stars

316. Icinga/icingaweb2・395 stars

317. mikeboers/PyAV・394 stars

318. pencil2d/pencil・390 stars

319. bit-team/backintime・389 stars

320. ethereum/browser-solidity・381 stars

321. OpenXRay/xray-16・377 stars

322. atom/github・375 stars

323. Storj/core・374 stars

324. partkeepr/PartKeepr・372 stars

325. awesome-jobs/vietnam・371 stars

326. kubernetes-helm/monocular・370 stars

327. symfony-cmf/cmf-sandbox・366 stars

328. magefile/mage・364 stars

329. monero-project/kovri・360 stars

330. grena/gruik・358 stars

331. fossasia/loklak_search・357 stars

332. paragonie/airship・357 stars

333. openSUSE/osem・353 stars

334. redmatrix/hubzilla・348 stars

335. OpenPTT/OpenPTT・347 stars

336. kotcrab/vis-editor・342 stars

337. RocketChat/Rocket.Chat.iOS・336 stars

338. jsxc/jsxc・336 stars

339. threema-ch/threema-web・335 stars

340. mysociety/fixmystreet・333 stars

341. NUKnightLab/juxtapose・331 stars

342. codeforscience/sciencefair・329 stars

343. Etar-Group/Etar-Calendar・329 stars

344. Microsoft/pxt・326 stars

345. LLK/scratch-www・325 stars

346. theia-ide/theia・323 stars

347. byte-foundry/prototypo・322 stars

348. internetarchive/openlibrary・319 stars

349. aurelia/cli・317 stars

350. ZenHubIO/support・311 stars

351. haskell-foundation/foundation・308 stars

352. Storj/storjshare-gui・304 stars

353. OpenUserJS/OpenUserJS.org・304 stars

354. cla-assistant/cla-assistant・302 stars

355. roadiz/roadiz・301 stars

356. kbenoit/quanteda・300 stars

357. Spomky-Labs/jose・300 stars

358. nguillaumin/osmtracker-android・299 stars

359. vaadin/vaadin-grid・294 stars

360. ppy/osu-web・291 stars

361. humanmade/WordPress-Importer・288 stars

362. hotosm/osm-tasking-manager2・287 stars

363. Bionus/imgbrd-grabber・286 stars

364. lbryio/lbry-app・284 stars

365. AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet・282 stars

366. Glucosio/glucosio-android・276 stars

367. vinszent/gnome-twitch・276 stars

368. streetmix/streetmix・270 stars

369. CGCookie/retopoflow・265 stars

370. EasyRPG/Player・265 stars

371. coyim/coyim・264 stars

372. tylergaw/colorme・263 stars

373. nuttyartist/notes・261 stars

374. aframevr/aframe-inspector・259 stars

375. autolab/Autolab・256 stars

376. 500tech/mimic・253 stars

377. Kotlin/kotlinx.html・252 stars

378. php-censor/php-censor・249 stars

379. opencollective/opencollective・247 stars

380. ludumdare/ludumdare・245 stars

381. brave/browser-android-tabs・240 stars

382. refreshoxford/django-cbv-inspector・236 stars

383. steemit/condenser・235 stars

384. linkeddata/dokieli・234 stars

385. Microsoft/vscode-arduino・234 stars

386. sulu/sulu・234 stars

387. LLK/scratch-gui・234 stars

388. RocketChat/Rocket.Chat.Android・233 stars

389. Alanaktion/phproject・232 stars

390. nilmtk/nilmtk・232 stars

391. rambler-digital-solutions/rambler-it-ios・226 stars

392. Camelcade/Perl5-IDEA・225 stars

393. openopps/openopps-platform・222 stars

394. benbernard/RecordStream・222 stars

395. mysociety/alaveteli・219 stars

396. Sprytile/Sprytile・217 stars

397. enjalot/blockbuilder・216 stars

398. nunit/docs・215 stars

399. apex/static・215 stars

400. owncloud/music・211 stars

401. bardsoftware/ganttproject・211 stars

402. Automattic/sensei・210 stars

403. mysociety/mapit・208 stars

404. xibosignage/xibo・208 stars

405. Syonix/monolog-viewer・207 stars

406. OpenLiberty/open-liberty・207 stars

407. stelligent/mu・206 stars

408. hacktoberfest17/programming・205 stars

409. astroidmail/astroid・205 stars

410. 18F/18f.gsa.gov・204 stars

411. Philip-Scott/Notes-up・200 stars

412. caskdata/cdap・199 stars

413. nextcloud/calendar・199 stars

414. liberapay/liberapay.com・198 stars

415. atom/one-dark-ui・198 stars

416. Reedyn/Saga・197 stars

417. vector-im/riot-ios・196 stars

418. getgrav/grav-plugin-admin・195 stars

419. rsjaffe/MIDI2LR・195 stars

420. hakaru-dev/hakaru・193 stars

421. chromium/hstspreload.org・193 stars

422. GetDKAN/dkan・193 stars

423. Runalyze/Runalyze・192 stars

424. joakimskoog/AnApiOfIceAndFire・190 stars

425. monero-project/monero-gui・190 stars

426. RemoteTechnologiesGroup/RemoteTech・189 stars

427. ipfs-shipyard/peerpad・189 stars

428. snowleopard/alga・188 stars

429. atom/find-and-replace・187 stars

430. DMOJ/judge・185 stars

431. archimatetool/archi・184 stars

432. Storj/storjshare-daemon・184 stars

433. onury/accesscontrol・183 stars

434. propensive/rapture・183 stars

435. dtolnay/syn・182 stars

436. Vector35/binaryninja-api・182 stars

437. Automattic/wp-super-cache・180 stars

438. TrustWallet/trust-wallet-ios・180 stars

439. mroth/scmpuff・179 stars

440. wallabag/android-app・179 stars

441. decrypto-org/rupture・178 stars

442. trufont/trufont・177 stars

443. algorithmic-music-exploration/amen・175 stars

444. matrix-org/dendrite・175 stars

445. libratbag/libratbag・175 stars

446. Spreads/Spreads・174 stars

447. semperfiwebdesign/all-in-one-seo-pack・174 stars

448. nextcloud/bookmarks・172 stars

449. nightingale-media-player/nightingale-hacking・172 stars

450. vmware/docker-volume-vsphere・171 stars

451. lidarr/Lidarr・171 stars

452. uxbox/uxbox・168 stars

453. OpenRA/ra2・168 stars

454. Spacelog/Spacelog・167 stars

455. AdguardTeam/AdguardForiOS・167 stars

456. RestComm/Restcomm-Connect・165 stars

457. pychess/pychess・165 stars

458. camunda/camunda-modeler・164 stars

459. nextcloud/news・162 stars

460. nextcloud/ios・161 stars

461. codeforamerica/click_that_hood・160 stars

462. ejgallego/jscoq・159 stars

463. Trustroots/trustroots・157 stars

464. QubesOS/qubes-issues・157 stars

465. Microsoft/workbooks・157 stars

466. podlove/podlove-web-player・157 stars

467. publiclab/plots2・156 stars

468. magarena/magarena・156 stars

469. amilajack/popcorn-time-desktop・155 stars

470. quicwg/base-drafts・155 stars

471. balancemymoney/balance-open・154 stars

472. pixelated/pixelated-user-agent・152 stars

473. gap-system/gap・152 stars

474. inaturalist/inaturalist・152 stars

475. HabitRPG/habitica-ios・150 stars

476. lightninglabs/lightning-app・150 stars

477. yetibot/yetibot・149 stars

478. go-restruct/restruct・148 stars

479. nextcloud/nextcloudpi・142 stars

480. nextcloud/mail・140 stars

481. AdguardTeam/AdguardForAndroid・139 stars

482. smartchicago/chicago-atlas・139 stars

483. aaronpk/IndieAuth.com・138 stars

484. cloudflare/doca・138 stars

485. CaliOpen/Caliopen・138 stars

486. googlefonts/fontbakery・137 stars

487. juju/juju-gui・132 stars

488. ekylibre/ekylibre・131 stars

489. atom/settings-view・131 stars

490. rosedu/wouso・130 stars

491. vgstation-coders/vgstation13・129 stars

492. stefan-niedermann/nextcloud-notes・129 stars

493. AppleWin/AppleWin・129 stars

494. httpwg/http-extensions・129 stars

495. mozilla/fxa-content-server・128 stars

496. ZeroK-RTS/Zero-K・128 stars

497. clojure/clojure-site・127 stars

498. lewissbaker/cppcoro・126 stars

499. JohnCoatesOSS/Limitless・126 stars

500. OpenChemistry/tomviz・126 stars

PS: Don’t forget to read How to Contribute to Open Source.

PPS: Yes, I’m going to open-source my code. Give me a dozen days. I need to clean it and write a decent README file.

Open Source Design 500 was originally published in freeCodeCamp on Medium, where people are continuing the conversation by highlighting and responding to this story.

Super Mario Odyssey is quite possibly my favorite Mario game. So much so that I went out of my way to complete every last challenge. But one of them gave me more trouble than all the others combined: Jump-Rope Genius in the Metro Kingdom.

You don’t even need to move. You just need to successfully jump 100 times in succession. But the trick is every five jumps it speeds up until 50, until you’re jumping almost twice a second. Press jump too early and you fail. Press jump too late and you fail. Press jump for too long and… you guessed it, you fail.

After a few dozen or so failed attempts I started joking that I’d just build something to beat it for me… and as the days went by and I still hadn’t finished the challenge my joking turned more serious and I started wondering how to do it.

My first thought was to simply program an Arduino to bridge the connectors for the jump button on a Switch controller, but thankfully I checked the iFixit teardown first because Nintendo controllers since the Wii use dome switches instead of the conductive rubber pads, which makes that impossible (for some fun reading see the evolution of Nintendo controllers over the years).

I was mentally tossing up between buying an older GameCube controller (with adapter) which would be easy to hack, or using a solenoid to physically press a button on a Switch controller, both seemed like viable solutions, but after getting outbid on the first few GameCube controllers selling on eBay I settled on the solenoid route.

After completing 835 of the 836 unique challenges in Mario, I turned all my attention back to the final moon. In order to program something to beat it, first I’d need to measure the timing, so my intention was to record the screen and then count the frames. Before setting up a camera I put a few practice rounds in, and much to my horror, I actually beat the thing legitimately.

Having spent two weeks telling everyone I knew that I was going to program something to beat it (and having most of them scoff) losing the excuse to do so was pretty disappointing.

However being an adult, I realized that I didn’t really need an excuse to waste my time and money (that’s pretty much all we do), so express ordered an Arduino and the necessary components to start my project.

The first step was to figure out how to use an Arduino, which… was pretty straight forward actually, the online editor and tutorials are super easy, and after programming a few flashing LEDs I felt ready to go. The biggest hurdle was actually finding a USB-B cable because honestly who still uses those?

The second step was to figure out the timing, and I made it impressively difficult for myself. I thought I was being clever by recording from the overhead view, and could use the woman’s foot to align frames, when her hand touched her foot I’d call that a revolution, and I painstakingly went through QuickTime pressing the arrow keys to step a frame at a time and counting one, two, three… sixty-eight, sixty-nine, seventy.

The second and a half step was to realize the jump count was a more reliable measure, and that Final Cut Pro would show me the time and frame count, allowing me to really quickly scrub through the video.

Do this 50 times… and put all the results into a spreadsheet and you have the secret to Jump-Rope success. Those last 50 jumps? You need to do one every 0.58 seconds.

With timings completed I turned my attention to the electronic half of the problem, and fortunately someone who understands electronics (I definitely do not) had already shared how to control a solenoid with an Arduino.

For those who don’t know, a solenoid is really just a cylindrical coil of wire which when you run a current through produces a magnetic field. The name is interchangeable with a few things that use solenoids (the coil part) to do something more complex, in this case push a small metal rod. Turn on the power and the rod pushes out, turn it off and the spring moves it back.

I wired up a circuit with a simple switch and solenoid, and wrote a program that would loop through and trigger it, progressively shortening the timing as it progressed. Flipping the switch would start the loop, turning it off would reset.

This would enable me to manually run Mario into position and flip the switch to start, and also give me an easy way to retry if I messed up (which I anticipated would be often). After a few hours (and some tips from my brother) I had a working circuit!

At this point I’d basically assumed success, and then reality kicked in (or rather, kicked me). In my naiveté I’d assumed the solenoid would be able to trivially depress a Switch button, the one I bought was a 5V solenoid able to move 3mm and apply 80 grams of force, that seemed like a lot (it’s actually less than a single newton).

I held it against the controller and… nothing. No movement, the button refused the budge. Googling for how much force is needed to press a Switch controller yielded no results, and around my house I had no good tools to measure it with.

So, with no good tools, I went looking for some bad ones.

What about cooking measures? I filled 1/3 of a cup with water and balanced that above a button, no movement. I filled 1/2 of a cup with water and it depressed. So there’s your answer, a Joy-Con button needs somewhere between a third and half a cup of water.

Turning those back into real units, 1 cup = 250 ml and the easy thing about the metric system is that weight is derived from the volume of water. 250 ml is 250 grams, so my Joy-Con needed somewhere between 83 grams and 125 grams to depress.

Suddenly my 80 gram solenoid didn’t seem so underpowered, what if I… overpowered it? I was giving it the 5 volts it asked for, but I had a 9 volt power supply. The magnetic force of a solenoid increases with the voltage (actually it goes up with the square of the voltage) so at 9 volts my solenoid should be applying closer to 250 grams, or as I like to think about it, 1 cup of water!

Step four involved attaching the solenoid to the controller. Given how little thought I had put into planning this part, it was no surprise how inelegant the solution turned out. A few pieces of wood raised it over the other buttons, a few pieces of electrical tape held the wood in place, and a rubber band kept the solenoid in position.

I was finally ready to put it all to the test, I warped to the Metro Kingdom, ran up to the challenge, and prepared myself to bask in the sweet glory of my smug success.

And almost immediately failed… My timing was wrong. I manually tweaked a few of the timings in my code and got Mario closer, closer again, and closer still, until he could pretty reliably get to 86.

At that point instead of randomly tweaking things I recorded it playing and returned to Final Cut Pro to recount frames (this time focusing on how many frames nearer/further the rope was getting per 5 jump segment), and while I was a little off in a few places, as Mario was always getting to 50 the only thing requiring changing was the 50+ timing. I reduced it to a jump every 35.2 frames and tried again.

Success! 261 jumps. This felt like a huge victory, you can see in the video it easily trounced my meagre human effort of 102 jumps. I immediately went and woke my wife and tried to explain how cool it was, and when that failed to get me much adulation, resorted to telling my brother who was much more suitably impressed.

However, it’s a robot, why should 261 be a limit? Why can’t it be perfect? I analyzed the frames again and noticed the rope was catching up to Mario ever so slowly, he needed to go faster!

Reducing the timing from a jump every 35.2 frames to one every 35.15 frames (a change of just 0.14%) resulted in a much more successful Mario.

So successful that it was able to play the infuriating Mario Jump-Rope challenge for 35 minutes and 21 seconds before failing… setting a new high score (for me) of 3613.

At first I assumed it failed because my timing was still imperceptibly out, but upon closer inspection of the video it stayed perfectly in sync until it… long pressed! What a human mistake for a computer to make, instead of doing a short quick jump it held the button too long and sent Mario too high, he jumped at the right time but landed late.

In actuality I think it was that the poor solenoid was overheating, earlier in the night while I was playing with timings it had stopped running as well, I think driving it at almost twice the voltage was problematic. In the video you can even see that it pressed a second time during the jump at the correct timing.

As for the code? That was the simplest part. A mere 76 lines of code can play Mario better than me

For simplicities sake I measured all timings in how many frames between jumps, I could count the frames easily in the video, and then just divide by 60 to turn that into seconds.

The code calculates everything using dead reckoning from the time the challenge started, I assumed imprecisions in triggering any single jump would average out. Every loop the code calculates how many milliseconds should have elapsed before the next jump and if that threshold is met turns on the solenoid; there is a short duration that it keeps the solenoid on before resetting (maybe it needed to be shorter to avoid the long-press).

And that’s it… almost stupidly simple, fittingly so, given the nature of the jumping challenge.

I could try again but at almost 40 minutes per attempt I’m just not interested enough. Also, I’ve since discovered that someone went one step better than me, although in a slightly different direction.

Instead of physically pressing a button on their controller they use a library to simulate being a controller enabling them to trivially send signals. When they ran into the same timing challenge as me (only getting a few hundred jumps before failing — they were using the constant 35.18 for their final jumps) they solved that by programmatically monitoring to the video signal, checking the score region and when it changes do another jump. With this method they can reach the max score of 99,999!

You’d think with all of this that I’d have one of the highest scores in the game… you’d be wrong! Only a week ago I’d probably be in the top 100, but a bug has been discovered in the game that enables anyone to glitch this challenge, for almost no effort you can get unlimited jumps and over 10,000 people have now done so. Maybe if Nintendo patch this and reset the score board I’ll dust my solenoid off again, I feel if you can build something to play the game using only the controller itself then that’s kinda legitimate.

How I built a robot that can beat the Mario Odyssey Jump-Rope Challenge for you was originally published in freeCodeCamp on Medium, where people are continuing the conversation by highlighting and responding to this story.

24 Ways, the advent calendar for web geeks, started up again this week. Throughout December they’ll be publishing a wide range of posts all about web design, CSS and front-end development.

Chen Hui Jing has already written a great post about feature queries and Stephanie Drescher published a post today about a tool called sonarwhal
which identifies accessibility, performance and security issues, just to name a few.

Direct Link to Article — Permalink

24 Ways is a post from CSS-Tricks

Smartphones have eased the lives of many, and students are no exception. Check out the 7 best smartphone apps for students to help them learn and organize themselves.

This post was first published on eLearning Industry.

Here are 23 ways to implement and support informal learning within an online learning environment.

This post was first published on eLearning Industry.

JavaScript is the most popular programming language and has been since 2014, according to Stack Overflow Survey. It is no wonder that over 1/3rd of all developer jobs require some JavaScript knowledge. So, if you plan to work as a developer in the near future, you should be familiar with this extremely popular language.

The post’s purpose is to bring together all JavaScript concepts that are frequently brought up in developer interviews. It was written so you can review everything you need to know about JavaScript in a single place.

Types & Coercion

There are 7 built-in types: null, undefined , boolean, number, string, object and symbol (ES6).

All of these are types are called primitives, except for object.

• Null vs. Undefined

Undefined is the absence of a definition. It is used as the default value for uninitialized variables, function arguments that were not provided and missing properties of objects. Functions return undefined when nothing has been explicitly returned.

Null is the absence of a value. It is an assignment value that can be assigned to a variable as a representation of ‘no-value’.

• Implicit coercion

Take a look at the following example:

In this case, the string variable name is coerced to true and you have ‘Joey doesn’t share food!’ printed in our console. But how do you know what will be coerced to true and what will be coerced to false?

Falsy values are values that will be coerced to false when forced a boolean coercion on it.

Falsy values: "", 0, null, undefined, NaN, false.

Anything not explicitly on the falsy list is truthy — boolean coerced to true.

Yes. You read it right. Empty arrays, objects and functions are boolean coerced to true!

• String & Number coercion

The first thing you need to be aware of is the + operator. This is a tricky operator because it works for both number addition and string concatenation.

But, the *, / , and -operators are exclusive for numeric operations. When these operators are used with a string, it forces the string to be coerced to a number.

• == vs. ===

It is widely spread that == checks for equality and === checks for equality and type. Well, that is a misconception.

In fact, == checks for equality with coercion and === checks for equality without coercion — strict equality.

Coercion can be tricky. Take a look at the following code:

What would you expect for the following comparison?
console.log(a == b); (1)

This comparison actually returns True. Why?
What really happens under the hood is that if you are comparing a boolean with something other than a boolean, JavaScript coerces that boolean to a number and compares. (2)

This comparison is now between a number and a string. JavaScript now coerces that string to a number and compares both numbers. (3)

In this case, the final comparison 0 == 0 is True.

'0' == false   (1)
'0' == 0       (2)
 0  == 0       (3)

For a fully comprehension on how such comparisons are performed, you can check ES5 documentation here.

For a cheat sheet, you can click here.

Some tricky comparisons to look out for:

Value vs. Reference

Simple values (also known as primitives) are always assigned by value-copy: null, undefined , boolean, number, string and ES6 symbol.

Compound values always create a copy of the reference on assignment: objects, which includes arrays, and functions.

To copy a compound value by value, you need to make a copy of it. The reference does not point to the original value.

Scope

Scope refers to the execution context. It defines the accessibility of variables and functions in the code.

Global Scope is the outermost scope. Variables declared outside a function are in the global scope and can be accessed in any other scope. In a browser, the window object is the global scope.

Local Scope is a scope nested inside another function scope. Variables declared in a local scope are accessible within this scope as well as in any inner scopes.

You may think of Scopes as a series of doors decreasing in size (from biggest to smallest). A short person that fits through the smallest door — innermost scope — also fits through any bigger doors — outer scopes.

A tall person that gets stuck on the third door, for example, will have access to all previous doors — outer scopes — but not any further doors — inner scopes.

Hoisting

The behavior of “moving” var and function declarations to the top of their respective scopes during the compilation phase is called hoisting.

Function declarations are completely hoisted. This means that a declared function can be called before it is defined.

Variables are partially hoisted. var declarations are hoisted but not its assignments.

let and const are not hoisted.

Function Expression vs. Function Declaration

• Function Expression
  A Function Expression is created when the execution reaches it and is usable from then on — it is not hoisted.

• Function Declaration
  A Function Declaration can be called both before and after it was defined — it is hoisted.

Variables: var, let and const

Before ES6, it was only possible to declare a variable using var. Variables and functions declared inside another function cannot be accessed by any of the enclosing scopes — they are function-scoped.

Variables declared inside a block-scope, such as if statements and for loops, can be accessed from outside of the opening and closing curly braces of the block.

Note: An undeclared variable — assignment without var, let or const — creates a var variable in global scope.

ES6 let and const are new. They are not hoisted and block-scoped alternatives for variable declaration. This means that a pair of curly braces define a scope in which variables declared with either let or const are confined in.

A common misconception is that const is immutable. It cannot be reassigned, but its properties can be changed!

Closure

A closure is the combination of a function and the lexical environment from which it was declared. Closure allows a function to access variables from an enclosing scope — environment — even after it leaves the scope in which it was declared.

The above example covers the two things you need to know about closures:

1. Refers to variables in outer scope.
   The returned function access themessage variable from the enclosing scope.
2. It can refer to outer scope variables even after the outer function has returned.
   sayHiToJon is a reference to the greeting function, created when sayHi was run. The greeting function maintains a reference to its outer scope — environment — in which message exists.

One of the main benefits of closures is that it allows data encapsulation. This refers to the idea that some data should not be directly exposed. The following example illustrates that.

By the time elementary is created, the outer function has already returned. This means that the staff variable only exists inside the closure and it cannot be accessed otherwise.

Let’s go deeper into closures by solving one of the most common interview problems on this subject:
What is wrong with the following code and how would you fix it?

Considering the above code, the console will display four identical messages "The value undefined is at index: 4". This happens because each function executed within the loop will be executed after the whole loop has completed, referencing to the last value stored in i, which was 4.

This problem can be solved by using IIFE, which creates a unique scope for each iteration and storing each value within its scope.

Another solution would be declaring the i variable with let, which creates the same result.

Immediate Invoked Function Expression (IIFE)

An IIFE is a function expression that is called immediately after you define it. It is usually used when you want to create a new variable scope.

The (surrounding parenthesis) prevents from treating it as a function declaration.

The final parenthesis() are executing the function expression.

On IIFE you are calling the function exactly when you are defining it.

Using IIFE:

• Enables you to attach private data to a function.
• Creates fresh environments.
• Avoids polluting the global namespace.

Context

Context is often confused as the same thing as Scope. To clear things up, lets keep the following in mind:
Context is most often determined by how a function is invoked. It always refers to the value of this in a particular part of your code.
Scope refers to the visibility of variables.

Function calls: call, apply and bind

All of these three methods are used to attach this into function and the difference is in the function invocation.

.call() invokes the function immediately and requires you to pass in arguments as a list (one by one).

.apply() invokes the function immediately and allows you to pass in arguments as an array.

.call() and .apply() are mostly equivalent and are used to borrow a method from an object. Choosing which one to use depends on which one is easier to pass the arguments in. Just decide whether it’s easier to pass in an array or a comma separated list of arguments.

Quick tip: Apply for Array — Call for Comma.

Note: If you pass in an array as one of the arguments on a call function, it will treat that entire array as a single element.
ES6 allows us to spread an array as arguments with the call function.

char.knows.call(Snow, ...["nothing", "Jon"]);  // You know nothing, Jon Snow

.bind() returns a new function, with a certain context and parameters. It is usually used when you want a function to be called later with a certain context.

That is possible thanks to its ability to maintain a given context for calling the original function. This is useful for asynchronous callbacks and events.

.bind() works like the call function. It requires you to pass in the arguments one by one separated by a comma.

'this' keyword

Understanding the keyword this in JavaScript, and what it is referring to, can be quite complicated at times.

The value of this is usually determined by a functions execution context. Execution context simply means how a function is called.

The keyword this acts as a placeholder, and will refer to whichever object called that method when the method is actually used.

The following list is the ordered rules for determining this. Stop at the first one that applies:

• new binding — When using the new keyword to call a function, this is the newly constructed object.

• Explicit binding — When call or apply are used to call a function, this is the object that is passed in as the argument.
  Note: .bind() works a little bit differently. It creates a new function that will call the original one with the object that was bound to it.

• Implicit binding — When a function is called with a context (the containing object), this is the object that the function is a property of.
  This means that a function is being called as a method.

• Default binding — If none of the above rules applies, this is the global object (in a browser, it’s the window object).
  This happens when a function is called as a standalone function.
  A function that is not declared as a method automatically becomes a property of the global object.

Note: This also happens when a standalone function is called from within an outer function scope.

• Lexical this — When a function is called with an arrow function =>, this receives the this value of its surrounding scope at the time it’s created.
  this keeps the value from its original context.

Strict Mode

JavaScript is executed in strict mode by using the “use strict” directive. Strict mode tightens the rules for parsing and error handling on your code.

Some of its benefits are:

• Makes debugging easier — Code errors that would otherwise have been ignored will now generate errors, such as assigning to non-writable global or property.
• Prevents accidental global variables — Assigning a value to an undeclared variable will now throw an error.
• Prevents invalid use of delete — Attempts to delete variables, functions and undeletable properties will now throw an error.
• Prevents duplicate property names or parameter values — Duplicated named property in an object or argument in a function will now throw an error.
• Makes eval() safer — Variables and functions declared inside an eval() statement are not created in the surrounding scope.
• “Secures” JavaScript eliminating this coercion — Referencing a this value of null or undefined is not coerced to the global object. This means that in browsers it’s no longer possible to reference the window object using this inside a function.

`new` keyword

The new keyword invokes a function in a special way. Functions invoked using the new keyword are called constructor functions.

So what does the new keyword actually do?

1. Creates a new object.
2. Sets the object’s prototype to be the prototype of the constructor function.
3. Executes the constructor function with this as the newly created object.
4. Returns the created object. If the constructor returns an object, this object is returned.

What is the difference between invoking a function with the new keyword and without it?

Prototype and Inheritance

Prototype is one of the most confusing concepts in JavaScript and one of the reason for that is because there are two different contexts in which the word prototype is used.

• Prototype relationship
  Each object has a prototype object, from which it inherits all of its prototype’s properties.
  .__proto__ is a non-standard mechanism (available in ES6) for retrieving the prototype of an object (*). It points to the object’s “parent” — the object’s prototype.
  All normal objects also inherit a .constructor property that points to the constructor of the object. Whenever an object is created from a constructor function, the .__proto__ property links that object to the .prototype property of the constructor function used to create it.
  (*) Object.getPrototypeOf()is the standard ES5 function for retrieving the prototype of an object.
• Prototype property
  Every function has a .prototype property.
  It references to an object used to attach properties that will be inherited by objects further down the prototype chain. This object contains, by default, a .constructor property that points to the original constructor function.
  Every object created with a constructor function inherits a constructor property that points back to that function.

Prototype Chain

The prototype chain is a series of links between objects that reference one another.

When looking for a property in an object, JavaScript engine will first try to access that property on the object itself.

If it is not found, the JavaScript engine will look for that property on the object it inherited its properties from — the object’s prototype.

The engine will traverse up the chain looking for that property and return the first one it finds.

The last object in the chain is the built-in Object.prototype, which has null as its prototype. Once the engine reaches this object, it returns undefined.

Own vs Inherited Properties

Objects have own properties and inherited properties.

Own properties are properties that were defined on the object.

Inherited properties were inherited through prototype chain. Inherited properties are not enumerable (not accessible in a for/in loop).

Object.create(obj) — Creates a new object with the specified prototype object and properties.

Inheritance by reference

An inherited property is a copy by reference of the prototype object’s property from which it inherited that property.

If an object’s property is mutated on the prototype, objects which inherited that property will share the same mutation. But if the property is replaced, the change will not be shared.

Classical Inheritance vs. Prototypal Inheritance

In classical inheritance, objects inherit from classes — like a blueprint or a description of the object to be created — and create sub-class relationships. These objects are created via constructor functions using the new keyword.

The downside of classical inheritance is that it causes:
inflexible hierarchy
tight coupling problems
fragile base class problems
duplication problems
And the so famous gorilla/banana problem — “What you wanted was a banana, what you got was a gorilla holding the banana, and the entire jungle.”

In prototypal inheritance, objects inherit directly from other objects. Objects are typically created via Object.create(), object literals or factory functions.

There are three different kinds of prototypal inheritance:

• Prototype delegation — A delegate prototype is an object which is used as a model for another object. When you inherit from a delegate prototype, the new object gets a reference to the prototype and its properties.
  This process is usually accomplished by using Object.create().
• Concatenative inheritance — The process of inheriting properties from one object to another by copying the object’s prototype properties, without retaining a reference between them.
  This process is usually accomplished by using Object.assign().
• Functional inheritance — This process makes use of a factory function(*) to create an object, and then adds new properties directly to the created object.
  This process has the benefit of allowing data encapsulation via closure.
  (*)Factory function is a function that is not a class or constructor that returns an object without using the new keyword.

You can find a complete article on this topic by Eric Elliott here.

Favor composition over class inheritance

Many developers agree that class inheritance should be avoided in most cases. In this pattern you design your types regarding what they are, which makes it a very strict pattern.

Composition, on the other hand, you design your types regarding what they do, which makes it more flexible and reusable.

Here is a nice video on this topic by Mattias Petter Johansson

Asynchronous JavaScript

JavaScript is a single-threaded programming language. This means that the JavaScript engine can only process a piece of code at a time. One of its main consequences is that when JavaScript encounters a piece of code that takes a long time to process, it will block all code after that from running.

JavaScript uses a data structure that stores information about active functions named Call Stack. A Call Stack is like a pile of books. Every book that goes into that pile sits on top of the previous book. The last book to go into the pile will be the first one removed from it, and the first book added to the pile will be the last one removed.

The solution to executing heavy pieces of code without blocking anything is asynchronous callback functions. These functions are executed later — asynchronously.

The asynchronous process begins with an asynchronous callback functions placed into a Heap or region of memory. You can think of the Heap as an Event Manager. The Call Stack asks the Event Manager to execute a specific function only when a certain event happens. Once that event happens, the Event Manager moves the function to the Callback Queue. Note: When the Event Manager handles a function, the code after that is not blocked and JavaScript continues its execution.

The Event Loop handles the execution of multiple pieces of your code over time. The Event Loop monitors the Call Stack and the Callback Queue.

The Call Stack is constantly checked whether it is empty or not. When it is empty, the Callback Queue is checked if there is a function waiting to be invoked. When there is a function waiting, the first function in the queue is pushed into the Call Stack, which will run it. This checking process is called a ‘tick’ in the Event Loop.

Let’s break down the execution of the following code to understand how this process works:

1. Initially the Browser console is clear and the Call Stack and Event Manager are empty.
2. first() is added to the Call Stack.
3. console.log("First message") is added to the Call Stack.
4. console.log("First message") is executed and the Browser console displays “First message”.
5. console.log("First message") is removed from the Call Stack.
6. first() is remove from the Call Stack.
7. setTimeout(second, 0) is added to the Call Stack.
8. setTimeout(second, 0) is executed and handled by the Event Manager. And after 0ms the Event Manager moves second() to the Callback Queue.
9. setTimeout(second, 0) is now completed and removed from the Call Stack.
10. third() is added to the Call Stack.
11. console.log("Third message") is added to the Call Stack.
12. console.log("Third message") is executed and the Browser console displays “Third message”.
13. console.log("Third message") is removed from the Call Stack.
14. Call Stack is now empty and the second() function is waiting to be invoked in the Callback Queue.
15. The Event Loop moves second() from the Callback Queue to the Call Stack.
16. console.log("Second message") is added to the Call Stack.
17. console.log("Second message") is executed and the Browser console displays “Second message”.
18. console.log("Second message") is removed from the Call Stack.
19. second() is removed from the Call Stack.

Note: The second() function is not executed after 0ms. The time you pass in to setTimeout function does not relate to the delay of its execution. The Event Manager will wait the given time before moving that function into the Callback Queue. Its execution will only take place on a future ‘tick’ in the Event Loop.

Thanks and congratulations for reading up to this point! If you have any thoughts on this, feel free to leave a comment.

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