Node是否在所需模块中运行所有代码? [英] Does Node run all the code inside required modules?

问题描述

节点模块是否在需要时运行?

Are node modules run when they are required?

例如:您有一个foo.js文件，其中包含一些代码和一些导出.

For example: You have a file foo.js that contains some code and some exports.

当我通过运行以下代码导入文件时

When I import the file by running the following code

var foo = require(./foo.js);

文件foo.js中的所有代码是否都运行并仅在此之后导出?

is all the code inside the file foo.js run and only exported after that?

推荐答案

就像在浏览器的<script>中一样，只要您需要一个模块，就可以解析并执行代码.

Much like in a browser's <script>, as soon as you require a module the code is parsed and executed.

但是，取决于模块代码的结构，可能没有函数调用.

However, depending on how the module's code is structured, there may be no function calls.

例如:

// my-module-1.js
// This one only defines a function.
// Nothing happens until you call it.
function doSomething () {
    // body
}
module.exports = doSomething;


// my-module-2.js
// This one will actually call the anonymous
// function as soon as you `require` it.
(function () {
    // body
})();

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