web worker 是运行在后台的 JavaScript，不会影响页面的性能。
html:
w=new Worker("demo_workers.js");
w.onmessage=function(event){
document.getElementById("result").innerHTML=event.data;
};//onmessage 事件监听器
w.terminate();//终止
w = undefined;//
js:
var i=0;
function timedCount()
{
i=i+1;
postMessage(i);//向页面返回数据
setTimeout("timedCount()",500);
}
timedCount();
看案例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Web Workers</title>
</head>
<body>
<p>计数： <output id="result"></output></p>
<button οnclick="startWorker()">开始工作</button>
<button οnclick="stopWorker()">停止工作</button>
<p><strong>注意：</strong> Internet Explorer 9 及更早 IE 版本浏览器不支持 Web Workers.</p>
<script>
var w;
function startWorker() {
if(typeof(Worker) !== "undefined") {
if(typeof(w) == "undefined") {
w = new Worker("demo_workers.js");
}
w.onmessage = function(event) {
document.getElementById("result").innerHTML = event.data;
};
} else {
document.getElementById("result").innerHTML = "抱歉，你的浏览器不支持 Web Workers...";
}
}
function stopWorker()
{
w.terminate();
w = undefined;
}
</script>
</body>
</html>