一款进度条，它的外观是一条直线，末端有个小球，在进度变化时可以显示数字百分比，更可以用不同颜色来表示当前进度的状态。来看看效果图。
接下来我们来分析一下这款HTML5进度条的实现源码，篇幅有限，我们只挑核心的代码来说。
HTML代码很简单，构造一个进度条容器和数字百分比容器：
<div id="wrapper">
<div>
<div>0</div>
<span></span>
</div>
</div>
首先我们来对进度条的容器进行样式渲染，利用CSS3的渐变属性来实现不同进度变换颜色的效果：
.loader-container {
height: 6px;
width: 600px;
position: absolute;
top: 50%;
left: 50%;
margin-top: -3px;
margin-left: -300px;
background-color: transparent;
background-image: -webkit-linear-gradient(left, #5bd8ff, #ff0000);
background-image: -moz-linear-gradient(left, #5bd8ff, #ff0000);
background-image: -o-linear-gradient(left, #5bd8ff, #ff0000);
background-image: -ms-linear-gradient(left, #5bd8ff, #ff0000);
background-image: linear-gradient(left, #5bd8ff, #ff0000);
box-shadow: inset 0 -2px 2px rgba(0, 0, 0, 0.4);
border-radius: 3px 0 0 3px;
}
.loader-container:after {
content: "";
display: block;
position: absolute;
right: 0;
top: 50%;
width: 1em;
height: 1em;
border-radius: 50%;
margin-top: -0.5em;
margin-right: -1em;
background-image: -webkit-linear-gradient(top, #000000, #212121);
background-image: -moz-linear-gradient(top, #000000, #212121);
background-image: -o-linear-gradient(top, #000000, #212121);
background-image: -ms-linear-gradient(top, #000000, #212121);
background-image: linear-gradient(top, #000000, #212121);
}
接下来是末端小圆球的样式：
.loader-container.done:after {
background: Red;
}
.run .runner {
content: "";
position: absolute;
right: 0;
height: 100%;
width: 0%;
background-color: transparent;
background-image: -webkit-linear-gradient(top, #000000, #212121);
background-image: -moz-linear-gradient(top, #000000, #212121);
background-image: -o-linear-gradient(top, #000000, #212121);
background-image: -ms-linear-gradient(top, #000000, #212121);
background-image: linear-gradient(top, #000000, #212121);
animation: loader 10s linear;
}
这里也是利用的CSS3的渐变属性。
然后是数字百分比的样式属性，这里随着进度变化，数字百分比的颜色也会发生变化。
.meter {
position: absolute;
top: 0;
right: 0;
font-size: 2em;
margin-top: .3em;
color: #ff0000;
animation: meter 10s linear;
text-shadow: 0 -1px 0 #333333;
}
.meter:after {
content: "%";
}
最后，我们再来看看JS代码，其实js要完成的工作非常简单，只需要将CSS3渲染好的进度条动起来就好，看代码：
var Loader = function () {
var loader = document.querySelector('.loader-container'),
meter = document.querySelector('.meter'),
k, i = 1,
counter = function () {
if (i <= 100) {
meter.innerHTML = i.toString();
i++;
} else {
window.clearInterval(k);
}
};
return {
init: function (options) {
options = options || {};
var time = options.time ? options.time : 0,
interval = time/100;
loader.classList.add('run');
k = window.setInterval(counter, interval);
setTimeout(function () {
loader.classList.add('done');
}, time);
},
}
}();
Loader.init({
// If you have changed the @time in LESS, update this number to the corresponding value. Measured in miliseconds.
time: 10000
});
源码打包下载地址：http://xiazai.jb51.net/201403/tools/css3jdt.rar