http://bruce-xu.github.io/blogs/js/promise  ``` Document promise test --> function loadImg(src) { var promise = new Promise(function (resolve, reject) { var img = document.createElement('img') img.onload = function () { resolve(img) } img.onerror = function () { reject('图片加载失败') } img.src = src }) return promise } // var src = 'https://www.imooc.com/static/img/index/logo\_new.png' // var result = loadImg(src) // result.then(function (img) { // console.log(1, img.width) // return img // }, function () { // console.log('error 1') // }).then(function (img) { // console.log(2, img.height) // }) // var src = 'https://www.imooc.com/static/img/index/logo\_new.png' // var result = loadImg(src) // result.then(function (img) { // console.log(1, img.width) // return img // }).then(function (img) { // console.log(2, img.height) // }).catch(function (ex) { // // 统一捕获异常 // console.log(ex) // }) // var src1 = 'https://www.imooc.com/static/img/index/logo\_new.png' // var result1 = loadImg(src1) // var src2 = 'https://img1.mukewang.com/545862fe00017c2602200220-100-100.jpg' // var result2 = loadImg(src2) // result1.then(function (img1) { // console.log('第一个图片加载完成', img1.width) // return result2 // 重要！！！ // }).then(function (img2) { // console.log('第二个图片加载完成', img2.width) // }).catch(function (ex) { // console.log(ex) // }) var src1 = 'https://www.imooc.com/static/img/index/logo\_new.png' var result1 = loadImg(src1) var src2 = 'https://img1.mukewang.com/545862fe00017c2602200220-100-100.jpg' var result2 = loadImg(src2) Promise.all(\[result1, result2\]).then(function (datas) { console.log('all', datas\[0\]) console.log('all', datas\[1\]) }) Promise.race(\[result1, result2\]).then(function (data) { console.log('race', data) }) ```