fetch

  1. 默认不带cookie
  2. 谬误不会reject
  3. HTTP谬误（例如404 Page Not Found 或 500 Internal Server Error）不会导致Fetch返回的Promise标记为reject；.catch()也不会被执行。
  4. 想要准确的判断 fetch是否胜利，须要蕴含 promise resolved 的状况，此时再判断 response.ok是不是为 true

// 不反对间接设置超时, 能够用promise
function fetchTimeout(url, init, timeout = 3000) {

return new Promise((resolve, reject) => {    fetch(url, init)        .then(resolve)        .catch(reject);    setTimeout(reject, timeout);})

}
// 停止fetch
const controller = new AbortController();

fetch(

    'http://domain/service', {        method: 'GET',        signal: controller.signal    }).then(response => response.json()).then(json => console.log(json)).catch(error => console.error('Error:', error));

controller.abort();

interface IOptions {    url: string;    type?: string;    data: any;    timeout?: number;}function formatUrl(json) {    let dataArr = [];    json.t = Math.random();    for (let key in json) {        dataArr.push(`${key}=${encodeURIComponent(json[key])}`)    }    return dataArr.join('&');}export function ajax(options: IOptions) {    return new Promise((resolve, reject) => {        if (!options.url) return;        options.type = options.type || 'GET';        options.data = options.data || {};        options.timeout = options.timeout || 10000;            let dataToUrlstr = formatUrl(options.data);        let timer;            // 1.创立        let xhr;        if ((window as any).XMLHttpRequest) {            xhr = new XMLHttpRequest();        } else {            xhr = new ActiveXObject('Microsoft.XMLHTTP');        }            if (options.type.toUpperCase() === 'GET') {            // 2.连贯            xhr.open('get', `${options.url}?${dataToUrlstr}`, true);            // 3.发送            xhr.send();        } else if (options.type.toUpperCase() === 'POST') {            // 2.连贯            xhr.open('post', options.url, true);            xhr.setRequestHeader('ContentType', 'application/x-www-form-urlencoded');            // 3.发送            xhr.send(options.data);        }            // 4.接管        xhr.onreadystatechange = () => {            if (xhr.readyState === 4) {                clearTimeout(timer);                if (xhr.status >= 200 && xhr.status < 300 || xhr.status === 304) {                    resolve(xhr.responseText);                } else {                    reject(xhr.status);                }            }        }            if (options.timeout) {            timer = setTimeout(() => {                xhr.abort();                reject('超时');            }, options.timeout)        }        // xhr.timeout = options.timeout;        // xhr.ontimeout = () => {        //     reject('超时');        // }    });}