Promise.all 如何防止某一个promise失败而使整个promise失败

原理：

　　由于Promise内部实现中，是否resolve由内部成功数组的长度和传入数组的长度进行比较的，那么在给失败的Promise在catch的时候返回一个reolve状态就可以啦。

上代码：

　　正常失败情况：

let p1 = new Promise((resolve, reject) => { 
    setTimeout(resolve, 1000, 'one'); 
}); 
let p2 = new Promise((resolve, reject) => { 
    setTimeout(resolve, 2000, 'two'); 
});
let p3 = new Promise((resolve, reject) => {
    setTimeout(resolve, 3000, 'three');
});
let p4 = new Promise((resolve, reject) => {
    setTimeout(resolve, 4000, 'four');
});
let p5 = new Promise((resolve, reject) => {
    reject('错误');
})
  
Promise.all([p1, p2, p3, p4, p5]).then(values => { 
    console.log({values});
}, reason => {
    console.log({reason});// reject
});

 

 

　　处理后：

 

let p1 = new Promise((resolve, reject) => {
setTimeout(resolve, 1000, 'one');
});
let p2 = new Promise((resolve, reject) => {
setTimeout(resolve, 2000, 'two');
});
let p3 = new Promise((resolve, reject) => {
setTimeout(resolve, 3000, 'three');
});
let p4 = new Promise((resolve, reject) => {
setTimeout(resolve, 4000, 'four');
});
let p5 = new Promise((resolve, reject) => {
reject('错误');
})

function catchFun(items) {
　　return items.map(item => item.catch((err) => Promise.resolve(err)))
}

Promise.all(catchFun([p1, p2, p3, p4, p5])).then(values => {
　　console.log({values});
}, reason => {
　　console.log({reason}); // reject
});