exp.js

export let a = 10;

export let person = {name:'lily'}

export function test(){console.log("hello");}

export class Animal{

}

index.js

import {a} form './exp.js';

a = 100;//報錯 a是常量不能改

console.log(a) //10


===========

import {a,person} form './exp.js';

// a = 100;//報錯 a是常量不能改

//如果是基本型別，不能改，如果是物件如{a,person}就可以修改
 

person.name = 'mickey';//物件可以修改屬性
console.log(a) //10
console.log(person.name) //mickey

===========

import {a,person,Animal} form './exp.js';

let ani = new Animal();
console.log(ani)

匯入方式比較

index.js

import {exp} from './exp.js'
console.log(exp.a);
console.log(exp.Animal);

=============

一次性匯入某個檔案的所有模組並重新命名
import 
 
* as exp from './exp.js';

console.log(exp.a);
console.log(exp.Animal);

將所有要匯入的元素放入default裡面

// exp.js

let a = 10;
let person = {name:'tom'};
function test(){console.log('hello')};
class Animal{}

export default{
    a,person,test,Animal
}

//default只能使用一次

// index.js

import Exp from './exp.js';
console.log(Exp.a);
console.log(Exp.Animal);