一道字节面试题解

V2EX = way to explore

V2EX 是一个关于分享和探索的地方

现在注册

已注册用户请登录

推荐关注

Meteor

JSLint - a Javascript code quality tool

jsFiddle

D3.js

WebStorm

推荐书目

Javascript 权威指南第 5 版

Closure: The Definitive Guide

这是一个创建于 2033 天前的主题，其中的信息可能已经有所发展或是发生改变。

刚刚面了字节跳动, 题目都很(~~~~~~)基础, 但就是答得不好...视频一挂, 诶, 有好想法了 T.T

不行, 我非得把答案贴这儿, 可惜面试官不在我面前, 不然我非得告诉他, 你看, 这解答至少还凑合啊

// 题目是实现下列链式调用 const chain = new Chain() chain .eat() .sleep(1000) .eat() .sleep(1000) .work()

// 我原来用的 promise 把所有方法都包裹起来, 简直丑破天际... // 下面是新的解答 // 至于里面有些属性是不是要用 private 或者 protected 什么的, 我就懒得细究了 interface EatAction { name: "eat"; params: []; } interface SleepAction { name: "sleep"; params: [number]; } interface WorkAction { name: "work"; params: []; } type Action = EatAction | SleepAction | WorkAction class Chain { running = false actions: Action[] = [] trigger() { if (this.running) { return } const action = this.actions.shift() if (!action) { return } this.running = true switch (action.name) { case "eat": console.log("eat") this.running = false this.trigger() break case "work": console.log("work") this.running = false this.trigger() break case "sleep": setTimeout(() => { console.log("sleep") this.running = false this.trigger() }, action.params[0]) break default: break } } eat() { this.actions.push({ name: "eat", params: [], }) this.trigger() return this } sleep(n: number) { this.actions.push({ name: "sleep", params: [n], }) this.trigger() return this } work() { this.actions.push({ name: "work", params: [], }) this.trigger() return this } }

5 条回复

jason94

2020-06-01 22:15:25 +08:00

这样是不是简单一点

```ts
class Chain {
private actions: Function[] = [];
constructor() {
setTimeout(async () => {
for (const action of this.actions) {
await action.call(this);
}
});
}

eat() {
this.actions.push(() => console.log('eat'));

return this;
}

sleep(timeout: number) {
this.actions.push(() => {
console.log('sleep ', timeout);
return new Promise((resolve) =>
setTimeout(() => {
resolve();
}, timeout)
);
});
return this;
}
work() {
this.actions.push(() => console.log('work'));

return this;
}
}

const chain = new Chain();

chain.eat().sleep(1000).eat().sleep(1000).work();

```

xiaoming1992

2020-06-01 22:33:16 +08:00

@jason94 你这么写倒也挺好, 就是如果有在 constructor 之后才添加进去的事件, 就不会执行了, 如:
setTimeout(() => { chain.eat() }, 5000)

mxT52CRuqR6o5

2020-06-01 23:04:09 +08:00

```ts
class Chain{
constructor(promise){
if(promise){
this._promise=promise;
}else{
this._promise=Promise.resolve();
}
}
eat(){
return this._next(()=>{console.log('eat')});
}
work(){
return this._next(()=>{console.log('work')});
}
sleep(ms){
return this._next(async ()=>{
await new Promise(resolve=>setTimeout(resolve,ms))
});
}
_next(someAction){
const nextPromise=(async ()=>{
await this._promise;
await someAction();
})()
return new Chain(nextPromise);
}
}
```
我的思路，没测试，可能有 bug

treemonster

2020-06-01 23:06:56 +08:00

class Chain{
task=Promise.resolve()
eat() {
this.task=this.task.then(_=>console.log('eat'))
return this
}
work() {
this.task=this.task.then(_=>console.log('work'))
return this
}
sleep(t) {
this.task=this.task.then(_=>new Promise(r=>{
console.log('sleep', t)
setTimeout(r, t)
}))
return this
}
}

promise 写很简单

xiaoming1992

2020-06-02 00:00:33 +08:00

@mxT52CRuqR6o5 @treemonster 大概一瞄，应该是没什么问题的。我当时的思路就跟 4 楼的一样，可是写的丑多了。。。