问题
Is there a way to see the code behind a JavaScript's method? Not a javascript method from the website's .html or .js files, but JavaScript's internal methods.
For example:
- How can I see how JavaScript calculates the
offsetTopof an element?
回答1:
JavaScript is implemented by the browser, so it depends on the browser.
Google's browser, Chrome, is closed-source not open-source. Which means that you can't view their source code, including their implementation of JavaScript. But, Chrome's source code is based on Chromium's source code, which is open source. You can view all of its source code in its git repository here. See more about this Chrome-Chromium relationship at the bottom of my answer.
Mozilla's browser, Firefox, is open-source just like all of their projects. You can view all of the source code for Mozilla projects here. You'll find the code that implements JavaScript in Firefox right here.
For closed-source implementations of JavaScript, like Chrome's, you can never be sure exactly how each method works. By reading the documentation available (see below), you will be able to get the best available idea of how a method might be implemented.
Note that just because Chrome's source code is based off of the open source project, Chromium, that doesn't mean the source code is the same. Chrome could have made tweaks to to JavaScript methods, and we wouldn't know. I think that is unlikely though, and all of the differences between Chrome and Chromium are most likely listed on this wikipedia page, and a nice post is available here on AskUbuntu
You can learn a lot more about Chromium's source code here.
Chrome JS documentation
来源：https://stackoverflow.com/questions/36658654/source-code-of-implementation-javascript-internal-methods