class Promises { constructor( cb) { this. thenArr = []; //存放then函数里面的成功的函数和失败的函数 this. cb = cb; //promise中的回调函数 this. count = 0; //计数 this. returnText = null; //返回值 this. resolve = this. resolve. bind( this); this. reject = this. reject. bind( this); this. cb( this. resolve, this. reject); }
static all( promiseData) { let resultData = []; let errData = []; return new Promises(( res, rej) => { promiseData. forEach( i => { i. then( data => { resultData. push( data); test(); }, ( err) => { errData. push( err); testerr(); }) })
function test() { if ( promiseData. length === resultData. length) { res( resultData) } }   function testerr() { if ( errData. length > 0) { rej( errData[ 0]) } } }) }
static race( promiseData) { let resultData = []; let errData = []; return new Promises(( res, rej) => { promiseData. forEach( i => { i. then( data => { resultData. push( data); test(); }, ( err) => { errData. push( err); testerr(); }) })
function test() { if ( promiseData. length > resultData. length) { res( resultData) } }
function testerr() { if ( errData. length === errData. length) { rej( errData[ 0]) } } }) } resolve( data) { // 判断返回值的状态 // 1.返回值是promise //2.返回值是普通的 let rest = this. thenArr. slice( this. count) if ( this. returnText && this. returnText instanceof Promises) { rest. forEach( item => { this. returnText. then( item. okCb, item. errCn); }) return; } else if( this. returnText) { this. thenArr[ this. count]. okCb( this. returnText); } else { this. returnText = this. thenArr[ this. count]. okCb( data); } this. count++; if ( this. count < this. thenArr. length) { this. resolve( data); } } reject( err){ //如果失败，根据count执行当前then函数的失败函数 this. thenArr[ this. count]. errCn( err) //如果失败的then函数下面还有未执行的then函数，则直接调用下一个then函数的成功函数 this. count++ if( this. count< this. thenArr. length){ this. resolve() } } then( okCb, errCn) { this. thenArr. push({ okCb, errCn }) return this; } }


let pro1=() =>{ return new Promises(( resolve, reject) =>{ setTimeout(() =>{ reject( 1) }, 1000) }) }
let pro2=() =>{ return new Promises(( resolve, reject) =>{ setTimeout(() =>{ reject( 2) }, 2000) }) }
Promises. race([ pro1(), pro2()]). then(( data) =>{ console. log( data) },( err) =>{ console. log( err+ "2344") })

// new Promises((res, rej) => { // setTimeout(() => { // rej(123) // }, 1000) // }).then((data) => { // console.log(data) // }, (err) => { // console.log('err', err) // }).then((data) => { // return new Promise((res, rej) => { // res(456) // }) // }).then((data) => { // console.log(data) // })
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