2021-06-28 将多个异步方法同步执行

var p1 = function (){
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve('p1')
}, 1000);
})
}
var p2 = function (){
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve('p2')
}, 500);
})
}
var p3 = function (){
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve('p3')
}, 100);
})
}
var fnArr = [p2, p1, p3]
var run = function (arr, start = 0){
if(start > arr.length || start < 0) return; // 参数start不能超过 arr.length，不能为负数
var next = function (i){
if(i < arr.length){
var fn = arr[i];
fn().then(res => {
console.log(res);
i++;
next(i)
})
}
}
next(start)
}
run(fnArr)