68 lines
1.5 KiB
JavaScript
68 lines
1.5 KiB
JavaScript
import { square, diag } from './a.js';
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console.log(square(11)); // 121
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console.log(diag(4, 3)); // 5
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// promise 构造函数接受一个函数作为参数，该函数的两个参数分别是resolve,reject
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// 成功时调用resolve函数，失败时调用reject函数
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// const promise = new Promise(function(resolve, reject) {
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// // ... some code
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// if (/* 异步操作成功 */){
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// resolve(value);
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// } else {
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// reject(error);
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// }
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// });
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// promise.then(function(value) {
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// // success
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// }, function(error) {
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// // failure
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// })
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let promise = new Promise(function(resolve, reject) {
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console.log('Promise');
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resolve();
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});
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promise.then(function() {
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console.log('resolved.');
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});
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console.log('Hi!');
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const getJSON = function(url) {
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const promise = new Promise(function(resolve, reject){
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const handler = function() {
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if (this.readyState !== 4) {
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return;
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}
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if (this.status === 200) {
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resolve(this.response);
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} else {
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reject(new Error(this.statusText));
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}
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};
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const client = new XMLHttpRequest();
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client.open("GET", url);
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client.onreadystatechange = handler;
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client.responseType = "json";
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client.setRequestHeader("Accept", "application/json");
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client.send();
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});
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return promise;
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};
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getJSON("/posts.json").then(function(json) {
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console.log('Contents: ' + json);
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}, function(error) {
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console.error('出错了', error);
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}); |