promise优化回调地狱
<script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.6.0/jquery.js"></script> <script> const ID_BASE_URL = 'https://jsonplaceholder.typicode.com/todos' const ROBOT_IMG_BASE_URL = 'https://robohash.org' function getRobotId(num, callback) { $.get(`${ID_BASE_URL}/${num}`, (data) => { const id = data.id callback(id) }) } function createBobot(id) { const img = document.createElement('img') img.src = ROBOT_IMG_BASE_URL + `/${id}?size=200x200` document.body.appendChild(img) } function getRobotIdPromise(num) { const promise = new Promise((res, rej) => { $.get(`${ID_BASE_URL}/${num}`, (data) => { const id = data.id res(id) }) }) return promise } getRobotIdPromise(1) .then((id) => { createBobot(id) return getRobotIdPromise(2) }) .then((id) => { createBobot(id) return getRobotIdPromise(3) }) .then((id) => { createBobot(id) return getRobotIdPromise(4) }) .then((id) => { createBobot(id) return getRobotIdPromise(5) }) .then((id) => { createBobot(id) }) // 回调地狱 // getRobotId(1, (id) => { // createBobot(id) // getRobotId(2, (id) => { // createBobot(id) // getRobotId(3, (id) => { // createBobot(id) // getRobotId(4, (id) => { // createBobot(id) // getRobotId(5, (id) => { // createBobot(id) // }) // }) // }) // }) // }) </script>