const xhr = new XMLHttpRequest()
    
    xhr.timeout = 3000;
    xhr.ontimeout = () => {
        console.log('timeout');

    }

    xhr.open('GET', 'https://playlet.zonelian.com/api/microtime?zlsj=zlsj')
    xhr.onreadystatechange = () => {
        if (xhr.readyState === 4) {
            console.log('res:', xhr.response)
            console.log('URL:', xhr.responseURL)
            console.log('header', xhr.getResponseHeader('content-type'))
        }
    }
    xhr.send();
    //xhr.abort(); 取消请求

（应该不会有人类要我手写吧...）