// exportDemo.js
count = 1;
module.exports.count = count;
module.exports.Hello = function() {
 var name;
 this.setName = function(newName) {
 name = newName;
 }
 this.sayHello = function() {
 console.log("hello Mr." + name);
 }
 this.getId = function() {
 return count++
 }
}

// requireDemo.js
var {Hello} = require("./exportDemo")
var hello = new Hello();

hello.setName("Blank");
hello.sayHello();

var { Hello, count } = require('./exportDemo')
var hello = new Hello();
// 让count自增
console.log(hello.getId());
console.log(hello.getId());
// 发现获取的count还是原值
console.log(count)

// 真正的count其实是已经改了的
var newHello = new Hello();
console.log(newHello.getId())

var { Hello: newHello, count: newCount } = require('./exportDemo')
console.log(newCount, 'newCount');
// 再次require，取得的newHello和之前require的Hello指向同一个拷贝
console.log(newHello === Hello) 

// exportDemo.mjs
export let a = 1;

// importDemo.mjs
import {a} from './exportDemo.mjs'
console.log(a)

// exportDemo.mjs
export let counter = 1;
export function incCounter() {
 counter ++;
}

// importDemo.mjs
import { counter, incCounter } from './exportDemo.mjs'

incCounter();
console.log(counter)		// 打印结果为2，而不是初始值的1

(function(exports, require, module, __filename, __dirname) {
// Module code actually lives in here
});

// exportDemo.mjs
export let a = 1;
export const b = 2;
export let obj = {};

// importDemo.mjs
import { a, b } from './exportDemo.mjs'
console.log(a, b)
a = 1 // 报错，TypeError: Assignment to constant variable，export出来的值是一个只读引用
obj.x = 1	// 可以改变属性值

export { x: 1 }	// 报错，SyntaxError:Unexpected token，这是一个编译阶段的错误

// 正确写法
export default { x: 1 }

export function() {}	// 报错，SyntaxError: Unexpected token (

// 正确写法
export default function() {}

// a.js
exports.loaded = false;
var b = require('./b.js')
console.log("b in a is " + JSON.stringify(b))
exports.loaded = true;
console.log("a complete")

// b.js
exports.loaded = false;
var a = require('./a.js')
console.log("a in b is " + JSON.stringify(a))
exports.loaded = true;
console.log("b complete")

// main.js
var a = require('./a.js')
var b = require('./b.js')

console.log("a in main is" + JSON.stringify(a))
console.log("b in main is" + JSON.stringify(b))

// a.mjs
import { bar } from './b.mjs'

console.log(bar);
export let foo = 'foo from a.mjs'

// b.mjs
import { foo } from './a.mjs'

console.log(foo)

export let bar = 'bar from b.mjs'

// main.mjs
import { foo } from './a.mjs'
import { bar } from './b.mjs'

// a.mjs
import { bar } from './b.mjs'

console.log(bar());
export function foo() {
 return 'foo from a.mjs'
}

// b.mjs
import { foo } from './a.mjs'
console.log(foo());
export function bar() {
 return 'bar from b.mjs'
}

// main.mjs
import { foo } from './a.mjs'
import { bar } from './b.mjs'