JavaScript import/export

Posted 2020-08-20 Tong__Ming

定义模块

ES6之后，使用模块语法（import/export）时，每个文件都会成为它自己的模块，带有一个私有全名空间。顶层的函数和变量不会污染全局全名空间。要为其他模块暴露函数，类，和变量以便import的话，可以用export关键字。

// not exported
function somethingPrivate() {
    console.log(‘TOP SECRET‘)
}


export const PI = 3.14;

export function doSomething() {
    console.log(‘Hello from a module!‘)
}

function doSomethingElse(){ 
    console.log("Something else")
}

export {doSomethingElse}

export class MyClass {
    test() {}
}

import整个模块

import * as test from ‘./test‘

test.doSomething()

./test表示test.js的路径。

import命名成员

import {doSomething, MyClass, PI} from ‘./test‘

doSomething()

const mine = new MyClass()
mine.test()

console.log(PI)

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语法

import defaultMember from ‘module‘;


import { memberA, memberB, ... } from ‘module‘;


import * as module from ‘module‘;


import { memberA as a, memberB, ... } from ‘module‘;


import defaultMember, * as module from ‘module‘;


import defaultMember, { moduleA, ... } from ‘module‘;


import ‘module‘;