用JavaScript写一个进度条

var porpressBar = document.getElementById('progressBar')
        var info = document.getElementById('info')
        var barW = 0
        var id = setInterval(function(){
            barW+=2
            porpressBar.style.width = barW + 'px'
            info.innerText = barW/2 + '%'
            if(barW==200){
                clearInterval(id)
            }
        },500)

        console.log(screen.availHeight);
        console.log(screen.availWidth);

<div id="box">
        <div id="progressBar"></div>
    </div>
<span id="info">0%</span>

//style

        #box{

            width: 200px;

            height: 50px;

            border: 1px solid black;

        }

        #progressBar{

            height: 50px;

            background-color: red;

        }