feat: 优先级任务队列的三种实现方式

Author: ceilf6

JS/algorithm/lazyman.js

@@ -0,0 +1,215 @@
+// === 1 ===
+// Promise 链实现：通过维护一个 promise 链，每次调用方法追加 .then()
+function LazyManPromise(name) {
+    this.name = name
+    // 维护 this.promise 延迟启动的 Promise 作为链的起点，确保链式调用全部完成后，再开始执行任务
+    // new Promise() 创建时 立即执行 executor 函数
+    this.promise = new Promise(resolve => {
+        setTimeout(() => {
+            console.log(`I am ${this.name}`)
+            resolve()
+        }, 0)
+    })
+}
+
+LazyManPromise.prototype.rest = function (time) {
+    // 在现有 Promise 链后追加新的异步操作
+    this.promise = this.promise.then(() => {
+        return new Promise(resolve => {
+            setTimeout(() => {
+                console.log(`Wake up after ${time}s`)
+                resolve()
+            }, time * 1000)
+        })
+    })
+    return this // 返回 this 支持链式调用
+}
+
+LazyManPromise.prototype.firstRest = function (time) {
+    // 创建新的 Promise 链，将原链追加到后面
+    const oldPromise = this.promise
+    this.promise = new Promise(resolve => {
+        setTimeout(() => {
+            console.log(`Wake up after ${time}s`)
+            resolve()
+        }, time * 1000)
+    }).then(() => oldPromise)
+    return this
+}
+
+LazyManPromise.prototype.learn = function (what) {
+    this.promise = this.promise.then(() => {
+        console.log(`Learning ${what}`)
+    })
+    return this
+}
+
+function HardmanPromise(name) {
+    return new LazyManPromise(name)
+}
+
+console.log('=== Promise 链实现 ===')
+HardmanPromise("Tom").rest(1).learn("Math")
+
+setTimeout(() => {
+    console.log('\n=== Promise firstRest 测试 ===')
+    HardmanPromise("Jack").firstRest(1).learn("English")
+}, 3000)
+
+
+// === 2 ===
+// 通过 任务队列task,next() 进行管理
+function LazyMan(name) {
+    this.name = name
+    this.task = [() => {
+        console.log(`I am ${this.name}`)
+        this.next() // 执行完后继续下一个任务
+    }]
+
+    // 延迟启动，确保链式调用完成后再执行
+    setTimeout(() => {
+        this.next()
+    }, 0)
+}
+
+// 执行下一个任务
+LazyMan.prototype.next = function () {
+    const task = this.task.shift()
+    task && task.call(this) // 使用 call 绑定 this
+}
+
+LazyMan.prototype.rest = function (time) {
+    this.task.push(() => {
+        setTimeout(() => {
+            console.log(`Wake up after ${time}s`)
+            this.next() // 休息结束后继续执行
+        }, time * 1000)
+    })
+    return this // 返回this进而支持装饰器模式链式调用，例如 .rest(time).rest()/.learn
+}
+
+LazyMan.prototype.firstRest = function (time) {
+    this.task.unshift(() => {
+        setTimeout(() => {
+            console.log(`Wake up after ${time}s`)
+            this.next()
+        }, time * 1000)
+    })
+    return this
+}
+
+LazyMan.prototype.learn = function (what) {
+    this.task.push(() => {
+        console.log(`Learning ${what}`)
+        this.next() // 执行完后继续
+    })
+    return this
+}
+
+// 工厂函数
+function Hardman(name) {
+    return new LazyMan(name)
+}
+
+// 测试
+console.log('=== 原型链实现 ===')
+Hardman("jack").rest(2).learn("computer")
+
+
+// === 3 ===
+// 任务队列的类实现
+class LazyMan2 {
+    constructor(name) {
+        this.name = name
+        this.tasks = [] // 任务队列
+
+        // 添加初始任务
+        this.tasks.push(() => {
+            console.log(`I am ${this.name}`)
+            this.next()
+        })
+
+        // 在下一个事件循环中开始执行任务队列
+        setTimeout(() => {
+            this.next()
+        }, 0)
+    }
+
+    // 执行下一个任务
+    next() {
+        const task = this.tasks.shift()
+        task && task()
+    }
+
+    // 休息
+    rest(time) {
+        this.tasks.push(() => {
+            setTimeout(() => {
+                console.log(`Wake up after ${time}s`)
+                this.next()
+            }, time * 1000)
+        })
+        return this // 返回 this 支持链式调用
+    }
+
+    // 优先休息（插入队列头部）
+    firstRest(time) {
+        this.tasks.unshift(() => {
+            setTimeout(() => {
+                console.log(`Wake up after ${time}s`)
+                this.next()
+            }, time * 1000)
+        })
+        return this
+    }
+
+    // 学习
+    learn(subject) {
+        this.tasks.push(() => {
+            console.log(`Learning ${subject}`)
+            this.next()
+        })
+        return this
+    }
+
+    // 吃东西
+    eat(food) {
+        this.tasks.push(() => {
+            console.log(`Eat ${food}`)
+            this.next()
+        })
+        return this
+    }
+}
+
+// 工厂函数
+function Hardman2(name) {
+    return new LazyMan2(name)
+}
+
+// 测试用例
+console.log('=== Test 1 ===')
+Hardman2("jack").rest(2).learn("computer")
+/*打印：
+I am jack
+Wake up after 2s
+Learning computer */
+
+// setTimeout(() => {
+//     console.log('\n=== Test 2 ===')
+//     Hardman("jack").firstRest(2).learn("computer")
+//     /* 打印：
+//     Wake up after 2s
+//     I am jack
+//     Learning computer */
+// }, 5000)
+
+// setTimeout(() => {
+//     console.log('\n=== Test 3 ===')
+//     Hardman("Tom").eat("lunch").rest(1).learn("English")
+//     /* 打印：
+//     I am Tom
+//     Eat lunch
+//     Wake up after 1s
+//     Learning English */
+// }, 10000)