https://zinoui.com/blog/ajax-request-progress-bar

download() {
    var progressBar = document.getElementById("progress");
    var progressBar_value = document.getElementById("progressBar_value");
    var progressBar_max = document.getElementById("progressBar_max");

    var xhr = new XMLHttpRequest();
    xhr.open("GET", "/good4/1.jpg?" + Math.floor(Math.random() * 99999), true);
    xhr.responseType = "text";
    xhr.onprogress = function (e) {
        console.log(e)
        if (e.lengthComputable) {
        progressBar.max = e.total;
        progressBar.value = e.loaded;
        progressBar_value.innerHTML = `${(e.loaded / 1024 / 1024).toFixed(3)}MB`;
        progressBar_max.innerHTML = `${(e.total / 1024 / 1024).toFixed(3)}MB`;
        }
    };
    xhr.onloadstart = function (e) {
        progressBar.value = 0;
    };
    xhr.onloadend = function (e) {
        progressBar.value = e.loaded;
    };
    xhr.send(null);
}

let num = 0
const imageObj = new Image();
const timer = setInterval(() => {
    document.getElementById('time').innerHTML = num++
    imageObj.onload = () => {
      document.getElementById('img').src = imageObj.src
      console.log(num)
      clearInterval(timer);
    }
},1000)

imageObj.src = 'http://good1230.com/templates/test_img/1.jpg';

const text = `日志异常内容：${err}`
const blob = new Blob([text], {type: 'text/plain'});
let formData = new FormData();
  formData.append("file", blob, `${new Date().getTime()}.txt`);

uploadException(formData).then(res => {

})

//detect the language preference of the user's browser
var userLanguage = window.navigator.userLanguage || window.navigator.language;

//gets the type of browser
function detectBrowser() { 
    if((navigator.userAgent.indexOf("Opera") || navigator.userAgent.indexOf('OPR')) != -1 ) {
        return 'Opera';
    } else if(navigator.userAgent.indexOf("Chrome") != -1 ) {
        return 'Chrome';
    } else if(navigator.userAgent.indexOf("Safari") != -1) {
        return 'Safari';
    } else if(navigator.userAgent.indexOf("Firefox") != -1 ){
        return 'Firefox';
    } else if((navigator.userAgent.indexOf("MSIE") != -1 ) || (!!document.documentMode == true )) {
        return 'IE';//crap
    } else {
        return 'Unknown';
    }
} 

function reverse_a_number(n)
{
  n = n + "";
  return n.split("").reverse().join("");
}
console.log(reverse_a_number(32243));

function coinFlip() {
 return (Math.floor(Math.random() * 2) == 0) ? 'heads' : 'tails';
}

window.navigator.userAgent

 function sleep(milliseconds) {
    return new Promise(resolve => setTimeout(resolve, milliseconds));
 }
 async function fun() {
    document.write('Hello World');
    for (let i = 1; i <=10 ; i++) {        
       await sleep(2000);
       document.write( i + " " + "Welcome to the javaTpoint.com" + " " + "</br>");
    }
 }
 fun();