如何阅读“原生代码”JavaScript 函数？

有什么方法可以看到 JavaScript 本机代码的声明吗？每当我试图在 Chrome 或 Firefox 中查看一个本地函数时，它都会显示“ native code”:

> String.fromCharCode
function fromCharCode() { [native code] }

这是什么意思，有没有什么工具可以帮助我阅读实际的代码？

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Not within the JavaScript environment, but you can view the source for the open-source implementations.

Google V8: http://code.google.com/p/v8/source/browse

Mozilla SpiderMonkey: https://developer.mozilla.org/en/SpiderMonkey

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最佳答案

The reason Chrome or Firefox says that the code is native is that it really is native - the WebKit and Firefox developers have coded up that functionality in C or C++, not JavaScript. However, if you want to see the actual code, you can look at the source repositories for Chromium and Firefox.

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Firefox now supports the inspection of "[native code]" objects via standard dev tools.

To see it in action:

  1. update Firefox (definitely works w/ v68+, may work with older versions as well)
  2. open dev tools
  3. go to the Console
  4. type the name of a native object, e.g., "Document"
  5. hit return
  6. go nuts on all those little dropdown arrows

FireFox - inspect "native code" - Document object

Chrome still returns ƒ Document() { [native code] }, unfortunately.

Chrome - DON'T inspect "native code" - disappointment

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Chromium Code Search provides a good way to read javascript native code. This post addresses a litter bit about how to use it. And in this video, you can see an example.


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