手写PromiseAll

最直接的思路, 依次执行即可; 不能用push, 因为返回的时间不好控制;

function PromiseAll(promises){

    return new Promise((resolve,reject)=>{
        let arr = Array.from(promises);
        let len = arr.length;

        let res = [];
        let count = 0;

        for(let i=0;i<len;i++){
            Promise.resolve(arr[i]).then(item=>{
                
                res[i]=item; // 这样写是为了控制先后完成的顺序;

                if(++count === len){
                    resolve(res);
                }
            }).catch(e=>reject(e));
        }
    })
}

使用Ts的版本：

function PromiseAll<T>(promises: Promise<T>[]): Promise<T[]> {
    const arr = Array.from(promises);
    let count = 0;
    const res: T[] = [];
    return new Promise((resolve, reject) => {
        for (let i = 0; i < arr.length; i++) {
            Promise.resolve(arr[i]).then((item) => {
                res[i] = item;

                if (++count === arr.length) {
                    resolve(res);
                }
            }).catch((e) => reject(e));
        }
    });
}

测试用例

// 测试用例 1: 所有 Promise 都成功
let promises1 = [
    Promise.resolve(1),
    Promise.resolve(2),
    Promise.resolve(3)
];

PromiseAll(promises1).then(result => {
    console.log(result); // 输出: [1, 2, 3]
}).catch(error => {
    console.error(error);
});

// 测试用例 2: 一个 Promise 失败
let promises2 = [
    Promise.resolve(1),
    Promise.reject('error'),
    Promise.resolve(3)
];

PromiseAll(promises2).then(result => {
    console.log(result);
}).catch(error => {
    console.error(error); // 输出: error
});

// 测试用例 3: 空数组
let promises3 = [];

PromiseAll(promises3).then(result => {
    console.log(result); // 输出: []
}).catch(error => {
    console.error(error);
});

// 测试用例 4: 混合值和 Promise
let promises4 = [
    1,
    Promise.resolve(2),
    3
];

PromiseAll(promises4).then(result => {
    console.log(result); // 输出: [1, 2, 3]
}).catch(error => {
    console.error(error);
});