【回馈牛客】腾讯+网易前端面经

Promise.all = (list) => {
    return new Promise((resolve,reject) => {
        const results = [];
        let count = 0;
        list.forEach((item, index) => {
            item.then((res) => {
                results[index] = res;
                if (++count === list.length) {
                    resolve(results);
                }
            }, (rej) => reject(rej));
        });
    });
}

const foo = async () => {
    const foo1 = new Promise((resolve) => setTimeout(resolve, 1000)).then(() => { console.log(1); });
    const foo2 = new Promise((resolve) => setTimeout(resolve, 1000)).then(() => { console.log(2); });
    await foo1;
    await foo2;
}

Access-Control-*

OPTIONS /cors HTTP/1.1 Origin: http://www.demo.com  -->表示请求来自哪个源。 Access-Control-Request-Method: PUT  -->该字段是必须的，用来列出浏览器的CORS请求会用到哪些HTTP方法，上例是PUT。 Access-Control-Request-Headers: X-Custom-Header  -->该字段是一个逗号分隔的字符串，指定浏览器CORS请求会额外发送的头信息字段，上例是X-Custom-Header。 Host: api.alice.com

function reverse(array, start, end) {
    let i, j;
    for(i = start, j = end; i <= j; i++, j--) {
        [array[i], array[j]] = [array[j], array[i]];
    }
}

<ul>
    <li></li>
    ...
</ul>

document.querySelector('ul').addEventListener('click', (e) => {
    console.log(e.target.textContent) })