Get Low-Level

Understanding Browsers, Specs
& Standards Bodies

<h4>On the whiteboard:</h4>
<p><i>list all libraries & frameworks you've used</i></p>
<ul>
  <li>look through the lesson plans listed on the frontend site</li>
  <li>look through your `package.json` files in projects you've built</li>
</ul>
<p><i>Learning 100 different libraries is still easier<br />than building an application with none.</i></p>

Identifying the Layers

<h3>Layer #3 - The Library</h3>
<ul>
  <li>previously used <a href="http://dexie.org/">Dexie</a> - library wrapping IndexedDB</li>
  <li><a href="https://github.com/turingschool-examples/markdown-previewer/blob/04-after-db/public/indexedDB.js">code</a> was concise and read similar to English</li>
</ul>
<h4>On Your Own:</h4>
<p>look through the Dexie <a href="https://github.com/dfahlander/Dexie.js">source code</a><br />and find the following implementations:</p>
<ul>
  <li>`put`</li>
  <li>`get`</li>
  <li>`delete`</li>
</ul>
<h3>Layer #2 - The Web API</h3>
<ul>
  <li>Downsides of IndexedDB: "The API is <a href="https://github.com/turingschool-examples/offline-news/blob/d6182e5e7858af7481ef41d534dbc5a5d8b717f0/public/indexedDB.js">brutal</a>".</li>
  <li>code is verbose and difficult to read</li>
</ul>
<h3>But y tho?</h3>
<ul>
  <li>Web APIs need to be <b>flexible</b> to handle many scenarios</li>
  <li>This means they have to be as <b>bare-bones</b> as possible</li>
</ul>
<h3>Layer #1 - The Browser</h3>
<ul>
  <li>browsers are made up of many different parts</li>
  <li>working with APIs is dependent on the built-in JavaScript Engine and Browser Engine</li>
</ul>
<h3>Browser Architecture</h3>
<img src="../../assets/images/lessons/get-low-level/browser-arch.png" />
<h3>Layer #1a - The Browser Engine</h3>
<p><i>The browser engine is responsible for implementing Web APIs and functionality like IndexedDB, geolocation, web audio, etc.</i></p>
<ul>
  <li>Chrome - Webkit (C++)</li>
  <li>Firefox - Gecko (C++)</li>
</ul>
<h3>Check the <a href="https://github.com/WebKit/webkit/tree/master/Source/WebCore/Modules">source</a></h3>
<ul>
  <li>which modules sound familiar to you?</li>
  <li>bump up a directory and explore the rest of /WebCore/</li>
  <li>what other APIs live in the browser engine?</li>
</ul>
<h3>Layer #0a - The Web API Specification</h3>
<p><i>The specification for a Web API gives platform engineers a strict set of rules for how the API should behave, which guides how it is implemented in the browser</i></p>
<ul>
  <li>spec writers agree on functional behavior</li>
  <li>platform engineers implement the API in the browser</li>
  <li>app developers build applications using the API</li>
</ul>
<h3><a href="https://www.w3.org/TR/IndexedDB/">IndexedDB Spec</a></h3>
<p><i>Specs are notoriously difficult for app developers to read because they are written for platform engineers who write C++</i></p>
<h3>Reverse!</h3>
<p><i>Let's walk through a single point of IndexedDB functionality from the bottom up.</i></p>
<h4>Opening a Database:</h4>
<ul>
  <li><a href="https://www.w3.org/TR/IndexedDB/#open-a-database">The Spec</a></li>
  <li><a href="https://github.com/WebKit/webkit/blob/master/Source/WebCore/Modules/indexeddb/IDBFactory.cpp#L75-L101">The Browser Engine Implementation</a></li>
  <li><a href="https://github.com/turingschool-examples/offline-news/blob/d6182e5e7858af7481ef41d534dbc5a5d8b717f0/public/indexedDB.js#L3-L21">Our JavaScript Implementation</a></li>
  <li><a href="https://github.com/turingschool-examples/markdown-previewer/blob/04-after-db/public/indexedDB.js#L3">The Dexie Library Wrapper</a></li>
</ul>
<h3>Standards Bodies</h3>
<p><i>Standards bodies facilitate creating technical documents that define how proposed web functionality should be implemented.</i></p>
<ul>
  <li><a href="https://www.w3.org/">W3C</a> - World Wide Web Consortium</li>
  <li><a href="https://whatwg.org/">WHATWG</a> - Web Hypertext Application Technology Working Group</li>
</ul>
<h3>Why Standards?</h3>
<ul>
  <li>promote a more stable and consistent web</li>
  <li>follow patterns that make implementation and maintenance easier</li>
  <li>are developed with all demographics in mind</li>
  <li>make it easier to share common knowledge and learn from each other</li>
</ul>
<h3>Standardization Process</h3>
<ul>
  <li><b>"Working Groups"</b> (clubs of old white men) are formed and discuss new ideas for Web APIs</li>
  <li><b>"Working Draft" (WD) -</b> document to be reviewed by the community</li>
  <li><b>"Candidate Recommendation" (CD) -</b> released for implementation experience</li>
  <li><b>"Proposed Recommendation" (PD) -</b> technical report sent to advisory board</li>
  <li><b>"W3C Recommendation" (REC) -</b> technical report endorsed by W3C members/directors</li>
</ul>
<h3>Web Incubator Community Group (WICG)</h3>
<p><i>WICG is a <a href="https://wicg.io/">Community Group</a> where people <a href="https://discourse.wicg.io/latest">discuss</a> changes to pre-existing APIs and pitch potential new ones. Some of the discussions include:</i></p>
<ul>
  <li><a href="https://discourse.wicg.io/t/web-share-api-for-sharing-content-to-arbitrary-destination/1561">Web Share</a></li>
  <li><a href="https://discourse.wicg.io/t/a-zip-api-in-the-browser/14">Zip</a></li>
  <li><a href="https://discourse.wicg.io/t/passing-an-object-of-attributes-to-document-createelement-as-the-second-argument/809">Changes to document.createElement()</a></li>
  <li><a href="https://discourse.wicg.io/t/wake-lock-api-suppressing-power-management-screensavers/769/3">Wake Lock API</a></li>
</ul>
<h3>Layer #1b - The JS Engine</h3>
<p><i>The JavaScript Engine is responsible for interpreting the JavaScript we write and doing something meaningful with it.</i></p>
<ul>
  <li>Chrome - V8 (C++)</li>
  <li>Firefox - Spidermonkey (C/C++)</li>
</ul>
<h3>Check the <a href="https://github.com/v8/v8/tree/master/src/js">source</a></h3>
<ul>
  <li>which file names sound familiar to you?</li>
  <li>bump up a directory and explore the rest of /src/</li>
  <li>what other functionaliy lives in the JS engine?</li>
</ul>
<h3>Array Methods in V8</h3>
<ul>
  <li><a href="https://github.com/v8/v8/blob/f2bd913cd459854894447f5422a953d23fa4e7ba/src/runtime/runtime-array.cc#L527-L618">C++ Implementation of Array.indexOf()</a></li>
  <li><a href="https://github.com/v8/v8/blob/f2bd913cd459854894447f5422a953d23fa4e7ba/src/js/array.js#L113-L119">JS Implementation of Array Push & Pop</a></li>
</ul>

Layer #0b - The ECMAScript Spec

The ECMAScript spec defines the entire JavaScript language, and is very scary.