导读
IIFE
- 定义
IIFE: Immediately Invoked Function Expression，意为 立即调用的函数表达式
- 为什么需要
IIFE
CommonJS
AMD
CMD
UMD
ESM
// counter.mjs
let counter = 10;
export default counter;
// index.mjs
import myCounter from './counter.mjs';
myCounter += 1;
console.log(myCounter);
解析：引入的模块是只读的，不可修改
index.mjs:2 Uncaught TypeError: Assignment to constant variable.
at index.mjs:2:11
// index.js
console.log('running index.js');
import { sum } from './sum.js';
console.log(sum(1, 2));
// sum.js
console.log('running sum.js');
export const sum = (a, b) => a + b;
running sum.js
running index.js
3
import 命令是编译阶段执行，所以代码运行之前被导入的模块会先运行。
// index.js
console.log('running index.js');
const { sum } = require('./a.js');
console.log(sum(1, 2));
// sum.js
console.log('running sum.js');
exports.sum = (a, b) => a + b;
running index.js
running sum.js
3