Understanding chromium source code12/14/2023 ![]() Note: You can keep this in mind, but don’t do it if it leads to code duplication or less expressive code. Now every time we call this function, V8 needs to check not only one shape but iterate over several possibilities.įor the faster code, you can initialize objects with the same type and not change their structure too much. Let’s have a look at a simple example: function foo() ] Each node of the tree denotes a construct occurring in the code. The parser picks it up and creates an Abstract Syntax Tree (AST): a tree representation of the source code. There's a list of all JS tokens in the keywords.txt file. The scanner takes the JS file and converts it to the list of known tokens. This process is called parsing and consists of two parts: the scanner and the parser itself. Once the code is received, we need to change it in a way that the compiler can understand. This can be done via a network, cache, or service workers. The first thing V8 needs to do is to download the source code. We will work with a mirror of V8 on GitHub as it provides a convenient and well-known UI to navigate the codebase. We’ll work particularly with V8 because of its use in Node.js and Electron, but other engines are built in the same way.Įach step will include a link to the code responsible for it, so you can get familiar with the codebase and continue the research beyond this article. Every major browser has developed its own JS engine: Google's Chrome uses V8, Safari uses JavaScriptCore, and Firefox uses SpiderMonkey. The JavaScript engine executes and compiles JavaScript into native machine code. The JS engine is a big part of the browser – but we haven't gotten into those details yet. While continually monitoring dynamic changes via animation frames, Blink paints the content on your screen. It parses the DOM tree, resolves styles, and determines the visual geometry of all the elements. So it's split into a lot of modules responsible for different logic.Īnd two of the most important parts of a browser are the JavaScript engine and a rendering engine.īlink is a rendering engine that is responsible for the whole rendering pipeline including DOM trees, styles, events, and V8 integration. ![]() They make sure that everyone follows the same guidelines and doesn't have to support dozens of completely different environments.Ī modern browser is quite a complicated piece of software with a codebase of tens of millions of lines of code. W3C is an international community that develops open standards for the Web. They define and describe aspects of the World Wide Web. ![]() Web Standards are a set of rules that the browser implements. Let's recap a bit so we're ready to dive in here. In a previous article we learned how the browser is structured and got a high-level overview of Chromium. Today we’ll look under the hood of JavaScript's V8 engine and figure out how exactly JavaScript is executed. ![]()
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