exports 快捷方式

【exports shortcut】

exports 变量在模块的文件级作用域内可用，并且在模块被评估之前，它被赋值为 module.exports 的值。

【The exports variable is available within a module's file-level scope, and is assigned the value of module.exports before the module is evaluated.】

它允许使用快捷方式，因此 module.exports.f = ... 可以更简洁地写作 exports.f = ...。但是，需要注意的是，和任何变量一样，如果给 exports 赋予一个新值，它将不再与 module.exports 绑定：

【It allows a shortcut, so that module.exports.f = ... can be written more succinctly as exports.f = .... However, be aware that like any variable, if a new value is assigned to exports, it is no longer bound to module.exports:】

module.exports.hello = true; // Exported from require of module
exports = { hello: false };  // Not exported, only available in the module 拷贝

当 module.exports 属性被一个新对象完全替换时，通常也会重新赋值 exports：

【When the module.exports property is being completely replaced by a new object, it is common to also reassign exports:】

module.exports = exports = function Constructor() {
  // ... etc.
}; 拷贝

为了说明这种行为，想象一下这个假设的 require() 实现，它与 require() 实际上所做的事情非常相似：

【To illustrate the behavior, imagine this hypothetical implementation of require(), which is quite similar to what is actually done by require():】

function require(/* ... */) {
  const module = { exports: {} };
  ((module, exports) => {
    // Module code here. In this example, define a function.
    function someFunc() {}
    exports = someFunc;
    // At this point, exports is no longer a shortcut to module.exports, and
    // this module will still export an empty default object.
    module.exports = someFunc;
    // At this point, the module will now export someFunc, instead of the
    // default object.
  })(module, module.exports);
  return module.exports;
} 拷贝