（一）Promise 实现
const sleep = (timeout) => {
return new Promise(resolve => setTimeout(resolve, timeout));
};
sleep(1000).then(() => {
console.log("best Cindy");
});
（二）Generator
function* sleepGenerator(time) {
yield new Promise(function (resolve, reject) {
setTimeout(resolve, time);
});
};
sleepGenerator(1000).next().value.then(() => { console.log("best Cindy") });
（三）async await
function sleep(time) {
return new Promise(resolve => setTimeout(resolve,time))
};
async function output() {
let out = await sleep(1000);
console.log("best Cindy");
return out;
};
output();
（四）ES5
function sleep(callback,time) {
if(typeof callback === 'function')
setTimeout(callback,time)
};
function output(){
console.log("best Cindy");
};
sleep(output,1000);
