module.exports

• <Object>

module.exports 对象由 Module 系统创建。 有时这是不可接受的；许多人希望他们的模块成为某个类的实例。 为此，则将所需的导出对象赋值给 module.exports。 将所需的对象赋值给 exports 只会重新绑定本地的 exports 变量，这可能不是想要的。

例如，假设正在制作一个名为 a.js 的模块：

const EventEmitter = require('node:events');

module.exports = new EventEmitter();

// 做一些工作，一段时间后从模块本身触发 'ready' 事件。
setTimeout(() => {
  module.exports.emit('ready');
}, 1000);

然后在另一个文件中可以这样做：

const a = require('./a');
a.on('ready', () => {
  console.log('module "a" is ready');
});

赋值给 module.exports 必须立即完成。 不能在任何回调中完成。 以下不起作用：

x.js:

setTimeout(() => {
  module.exports = { a: 'hello' };
}, 0);

y.js:

const x = require('./x');
console.log(x.a);

• <Object>

The module.exports object is created by the Module system. Sometimes this is not acceptable; many want their module to be an instance of some class. To do this, assign the desired export object to module.exports. Assigning the desired object to exports will simply rebind the local exports variable, which is probably not what is desired.

For example, suppose we were making a module called a.js:

const EventEmitter = require('node:events');

module.exports = new EventEmitter();

// Do some work, and after some time emit
// the 'ready' event from the module itself.
setTimeout(() => {
  module.exports.emit('ready');
}, 1000);

Then in another file we could do:

const a = require('./a');
a.on('ready', () => {
  console.log('module "a" is ready');
});

Assignment to module.exports must be done immediately. It cannot be done in any callbacks. This does not work:

x.js:

setTimeout(() => {
  module.exports = { a: 'hello' };
}, 0);

y.js:

const x = require('./x');
console.log(x.a);