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Symbol.iterator与Symbol.asyncIterator并用Example let obj = { count: 0, items: { names: ['小明', '笑话', '小草'], age: [19,20,30], haha: ['小小', '大大'], }, Gen(time) { return new Promise((resolve, reject) => { setTimeout(function() { resolve({ done: false, value: time }) }, time) }) }, [Symbol.asyncIterator] () { let self = this return { next() { self.count++ if (self.count < 4) { return self.Gen(Math.random() * 1000) }else { return Promise.resolve({done: true, value: ''}) } } } }, [Symbol.iterator] () { let arr = this.items; let keys = Reflect.ownKeys(arr) let values = []; return { next() { if (!values.length) { if (keys.length) { values = arr[keys[0]] keys.shift() } else { return { done: true, value: '' } } } return { value: values.shift(), done: false } } } } } for (let i of obj) { console.log(i) } async function test() { for await (let i of obj) { console.log(i) } } test()
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ES9中的for await of function Gen(time) { return new Promise((resolve, reject) => { setTimeout(function () { resolve(time) },time) }) } async function test() { let arr = [Gen(2000), Gen(200), Gen(3000)] for(let i of arr) { console.log(Date.now()) console.log(Date.now(), await i.then(console.log)) console.log(Date.now()) } } test().then(() => {console.log('<<<======华丽分割线======>>>'); testTwo()}) async function testTwo() { let arr = [Gen(3000), Gen(300), Gen(2000)] for await (let i of arr) { console.log(Date.now(), i) } }
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使用Generator定义Symbol.iterator可迭代对象 let booksInfo = { authDescipt: { a: ['hello','book', 'san'], b: ['nihao', 'henhao', 'three'], c: ['aaa', 'bbb', 'ccc'] } } booksInfo[Symbol.iterator] = function *() { let AllAuthDescipt = this.authDescipt; let keys = Reflect.ownKeys(AllAuthDescipt) let values = [] while(1) { if (!values.length) { if (keys.length) { values = AllAuthDescipt[keys[0]] keys.shift() yield values.shift() } else { return false } }else { yield values.shift() } } } o = [] for (let v of booksInfo) { o.push(v) } console.log(o)
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使用Symbol.iterator定义可迭代对象 let booksInfo = { authDescipt: { a: ['hello','book', 'san'], b: ['nihao', 'henhao', 'three'], c: ['aaa', 'bbb', 'ccc'] } } booksInfo[Symbol.iterator] = function () { let AllAuthDescipt = this.authDescipt; let keys = Reflect.ownKeys(AllAuthDescipt) let values = [] return { next() { if (!values.length) { if (keys.length) { values = AllAuthDescipt[keys[0]] keys.shift() } } return { done: !values.length, value: values.shift(), } } } } for (let v of booksInfo) { console.log(v) // hello // index.js:31 book // index.js:31 san // index.js:31 nihao // index.js:31 henhao // index.js:31 three // index.js:31 aaa // index.js:31 bbb // index.js:31 ccc }