progress_bar/demo1.html

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <link href="loader.css" rel="stylesheet">
</head>
<body>
<div id="loader" class="loader">
    <div class="progress">
        <div class="progress-bar progress-bar-striped">
            <div class="progress-value"></div>
        </div>
    </div>
</div>
</body>
<script src="jquery.js"></script>
<script>
    var $bar = $('#loader').find('.progress-bar');
    var $value = $bar.find('.progress-value');

    var Task = function (index, duration) {
        setTimeout(function () {
            var p = (index / 4 * 100).toFixed(0) + '%';
            $bar.css('width',p);
            $value.text(p);
            console.log('第' + index + '个异步任务执行完毕');
        }, duration);
    };

    //模拟四个同时发起的异步任务
    var task1 = new Task(1, 1000);
    var task2 = new Task(2, 3000);
    var task3 = new Task(3, 5000);
    var task4 = new Task(4, 7000);
</script>
</html>