关键词： 闭包 异步 词法作用域 事件队列 es6 ....

(function print() {  for (var i = 0; i < 5; i++) {    setTimeout(() => console.log(i),i*1000)  }})()// 上面的方法 每隔1s打印 5(function print() {  for( let i = 0; i < 5; i++) {    setTimeout(() => console.log(i), i*1000)  }})()// 每隔一秒打印 0 1 2 3 4(function print() {  for(var i = 0; i < 5; i++) {    (function(i) {        setTimeout(() => console.log(i), i*1000)    })(i)  }})()// 每隔一秒打印 0 1 2 3 4function print(i) {  return new Promise((resolve, reject) => {    setTimeout(() => resolve(i), i*1000)  })}var arr = [];for (var i = 0; i < 5; i++) {  arr.push(print(i))}for (var i = 0; i < 5; i++) {  arr[i].then(data => console.log(data))}// 每隔一秒打印 0 1 2 3 4// promise是一个容器，里面包含着异步操作function print(i) {  return new Promise(resolve => {    setTimeout(() => resolve(i), 1000)  })}async function main() {  for(var i = 0; i < 5; i++) {    var r = await print(i)    console.log(r)  }}