手写实现 Promise.all 和 Promise.race

Promise.race_ = function(promiseList) {
    if (!Array.isArray(promiseList)) throw new Error('promiseList 必须是可迭代对象');
    return new Promise((resolve, reject) => {
        for (const p of promiseList) {
            Promise.resolve(p).then(res => resolve(res), err => reject(err));
        }
    });
}

Promise.all_ = function(promiseList) {
    if (!Array.isArray(promiseList)) throw new Error('promiseList 必须是可迭代对象');
    return new Promise((resolve, reject) => {
        const promiseNum = promiseList.length;
        let resovledCount = 0;
        const resolvedValues = new Array(promiseNum);
        promiseList.forEach((p, i) => {
            Promise.resolve(p).then(res => {
                resolvedValues[i] = res;
                resovledCount += 1;
                if (resovledCount === promiseNum) resolve(resolvedValues);
            }, err => reject(err));
        });
    });
}

function fakePromise(url, time, success = true) {
    return new Promise((resolve, reject) => {
        console.log(`${url} 开始`);
        setTimeout(() => {
            if (success) resolve(`${url} 成功`);
            else reject(`${url} 失败`);
        }, time * 1000);
    });
}

const promiseList = [
    fakePromise('1', 2),
    fakePromise('2', 3),
    fakePromise('3', 1),
    fakePromise('4', 2, false),
    fakePromise('5', 4),
    fakePromise('6', 2),
];

Promise.race_(promiseList).then(res => console.log(res), err => console.log(err));
Promise.all_(promiseList).then(res => console.log(res), err => console.log(err));