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這篇文章主要介紹“如何用promsie實現觀察者模式”，在日常操作中，相信很多人在如何用promsie實現觀察者模式問題上存在疑惑，小編查閱了各式資料，整理出簡單好用的操作方法，希望對大家解答”如何用promsie實現觀察者模式”的疑惑有所幫助！接下來，請跟著小編一起來學習吧！
下面我們用一個示例來演示一下什么是觀察者模式，有這樣一個場景，在一個院子里，有一個小偷，和若干條狗，小偷只要一行動，狗就會叫，這個場景如果用圖來展示的話如圖：
// 第一版class Thief {constructor(){}// thief的方法,調用dog的方法;action(){dog1.call()dog2.call()dog3.call()}}class Dog {call(){console.log("狗叫")}}let dog1 = new Dog()let dog2 = new Dog()let dog3 = new Dog()let thief = new Thief();thief.action()
// 第一版-新增dog4class Thief {constructor() {}// thief的方法,調用dog的方法;action() {dog1.call()dog2.call()dog3.call()// 新增代碼dog4.call()}}class Dog {call() {console.log("狗叫")}}let dog1 = new Dog()let dog2 = new Dog()let dog3 = new Dog()// 新增代碼:let dog4 = new Dog()let thief = new Thief();thief.action()
// 第二版// 1、thief增加了list屬性，是一個數組// 2、subscrible方法，追加方法// 3、publish 發布消息class Thief {constructor() {this.list = []}//subscrible(call) {this.list.push(call)}// publish遍歷數組,調用所有方法。publish() {for (let i = 0; i < this.list.length; i++) {this.list[i]()}}// thief的方法內部不會直接調用dog的方法了，// 而是調用publishaction() {this.publish()}}class Dog {call() {console.log("狗叫")}}let thief = new Thief();let dog1 = new Dog()thief.subscrible(dog1.call)// 每增加一條狗就將狗的call方法追加到listlet dog2 = new Dog()thief.subscrible(dog2.call)let dog3 = new Dog()thief.subscrible(dog3.call)thief.action()
// 第二版，新增dog4// 1、thief增加了list屬性，是一個數組// 2、subscrible方法，追加方法// 3、publish 發布消息class Thief {constructor() {this.list = []}//subscrible(call){this.list.push(call)}// publish遍歷數組,調用所有方法。publish(){for(let i= 0 ;i<this.list.length;i++){this.list[i]()}}// thief的方法內部不會直接調用dog的方法了，// 而是調用publishaction() {this.publish()}}class Dog {call() {console.log("狗叫")}}let thief = new Thief();let dog1 = new Dog()thief.subscrible(dog1.call)// 每增加一條狗就將狗的call方法追加到listlet dog2 = new Dog()thief.subscrible(dog2.call)let dog3 = new Dog()thief.subscrible(dog3.call)// 增加代碼：let dog4 = new Dog()thief.subscrible(dog4.call)thief.action()
// 第二版，新增thiefclass Thief {constructor() {this.list = []}//subscrible(call){this.list.push(call)}// publish遍歷數組,調用所有方法。publish(){for(let i= 0 ;i<this.list.length;i++){this.list[i]()}}// thief的方法內部不會直接調用dog的方法了，// 而是調用publishaction() {this.publish()}}class Dog {call() {console.log("狗叫")}}let thief = new Thief();// 新增thief代碼let thief1 = new Thief()let dog1 = new Dog()thief.subscrible(dog1.call)// 新增代碼thief1.subscrible(dog1.call)let dog2 = new Dog()thief.subscrible(dog2.call)// 新增代碼thief1.subscrible(dog2.call)let dog3 = new Dog()thief.subscrible(dog3.call)// 新增代碼thief1.subscrible(dog3.call)thief.action()// 新增代碼thief1.action()
class Pubsub{ constructor(){ this.list = [] } subscrible(call){ this.list.push(call) } publish(){ for(let i= 0 ;i<this.list.length;i++){ this.list[i]() } }}
let pubsub = new Pubsub();class Dog {call() {console.log("狗叫")}}class Thief {constructor() {}action() {pubsub.publish()}}let thief = new Thief();let dog1 = new Dog()pubsub.subscrible(dog1.call)let dog2 = new Dog()pubsub.subscrible(dog2.call)let dog3 = new Dog()pubsub.subscrible(dog3.call)thief.action()
let pubsub = new Pubsub();class Dog {call() {console.log("狗叫")}}class Thief {constructor() {}action() {pubsub.publish()}}let thief = new Thief();// 新增thief1代碼let thief1 = new Thief();let dog1 = new Dog()pubsub.subscrible(dog1.call)let dog2 = new Dog()pubsub.subscrible(dog2.call)let dog3 = new Dog()pubsub.subscrible(dog3.call)// 新增dog4代碼let dog4 = new Dog()pubsub.subscrible(dog4.call)thief.action()
class Pubsub { constructor() { let promise = new Promise((resolve,reject)=>{ this.resolve = resolve; }) this.promise = promise; } subscrible(call) { this.promise.then(call) } publish() { this.resolve(); }}
class Pubsub {constructor() {let promise = new Promise((resolve,reject)=>{this.resolve = resolve;})this.promise = promise;}subscrible(call) {this.promise.then(call)}publish() {this.resolve();}}let pubsub = new Pubsub();class Dog {call() {console.log("狗叫")}}class Thief {constructor() {}action() {pubsub.publish()}}let thief = new Thief();// 新增thief1代碼let thief1 = new Thief();let dog1 = new Dog()pubsub.subscrible(dog1.call)let dog2 = new Dog()pubsub.subscrible(dog2.call)let dog3 = new Dog()pubsub.subscrible(dog3.call)// 新增dog4代碼let dog4 = new Dog()pubsub.subscrible(dog4.call)thief.action()
const axios = require('axios')// 1、獲取CancelTokenvar CancelToken = axios.CancelToken;// 2、生成sourcevar source = CancelToken.source();console.log(source.token)axios.get('/user/12345', {//get請求在第二個參數 // 3、注入source.token cancelToken: source.token}).catch(function (thrown) { console.log(thrown)});axios.post('/user/12345', {//post請求在第三個參數 name: 'new name'}, { cancelToken: source.token}).catch(e => { console.log(e)});// 4、調用source.cancel("原因"),終止注入了source.token的請求source.cancel('不想請求了');
'use strict';var Cancel = require('./Cancel');/** * A `CancelToken` is an object that can be used to request cancellation of an operation. * * @class * @param {Function} executor The executor function. */function CancelToken(executor) { if (typeof executor !== 'function') { throw new TypeError('executor must be a function.'); } var resolvePromise; this.promise = new Promise(function promiseExecutor(resolve) { resolvePromise = resolve; }); var token = this; executor(function cancel(message) { if (token.reason) { // Cancellation has already been requested return; } token.reason = new Cancel(message); resolvePromise(token.reason); });}/** * Throws a `Cancel` if cancellation has been requested. */CancelToken.prototype.throwIfRequested = function throwIfRequested() { if (this.reason) { throw this.reason; }};/** * Returns an object that contains a new `CancelToken` and a function that, when called, * cancels the `CancelToken`. */CancelToken.source = function source() { var cancel; var token = new CancelToken(function executor(c) { cancel = c; }); return { token: token, cancel: cancel };};module.exports = CancelToken;
function CancelToken(executor) {var resolvePromise;this.promise = new Promise(function promiseExecutor(resolve) {resolvePromise = resolve;});var token = this;executor(function cancel(message) {if (token.reason) {return;}token.reason = messageresolvePromise(token.reason);});}CancelToken.source = function source() {var cancel;var token = new CancelToken(function executor(c) {cancel = c;});return {token: token,cancel: cancel};};
if (config.cancelToken) { // Handle cancellation config.cancelToken.promise.then(function onCanceled(cancel) { if (!request) { return; } request.abort(); reject(cancel); // Clean up request request = null; });}
config.cancelToken.promise.then(function onCanceled(cancel) { if (!request) { return; } request.abort(); reject(cancel); // Clean up request request = null;});
到此，關于“如何用promsie實現觀察者模式”的學習就結束了，希望能夠解決大家的疑惑。理論與實踐的搭配能更好的幫助大家學習，快去試試吧！若想繼續學習更多相關知識，請繼續關注億速云網站，小編會繼續努力為大家帶來更多實用的文章！
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