1 实现sleep函数 要求: 1 2 3 4 5 (async () => { console.log('hello') await sleep(2000) console.log('world') })() 题解 1 const sleep = (ms) => new Promise((resolve)=>setTimeout(resolve, ms)) 2 实现'Hello World!'.reverse() 1 String.prototype.reverse = function reverse() { return this.split('').reverse().join('')} 3 事件代理、监听、DOM自定