js 依次执行多个promise函数

const runPromisesInSeries = ps => ps.reduce((p, next) => p.then(next), Promise.resolve());

// 例子
const delay = d => new Promise(r => setTimeout(r, d));
// 依次执行每个Promise ，总共需要3秒钟才能完成
runPromisesInSeries([() => delay(1000), () => delay(2000)]);