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HTML5のWeb Worker

2016-02-13 12:55 561 查看

HTML5のWeb Worker

Web Worker简述

web worker 是运行在后台的 JavaScript，不会影响页面的性能。

使用步骤

1> 检查浏览器是否支持Web Worker

if (typeof Worker != "undefined") {
// support
} else {
// your browser does not support
}

2>创建Web Worker对象，执行后台任务

if (typeof worker == "undefined") {
worker = new Worker("task.js");
}
worker.onmessage = function(event) {
message = event.data;
detailSpan.innerHTML = message;
};

3> 终止Web Woker

function terminate() {
worker.terminate();
worker = undefined;
}

实例

使用按钮控制后台执行任务，html代码如下：

<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8">
<noscript>Your browser does not support JavaScript pluin</noscript>
<script type="text/javascript">
var worker;
var message = "";

function start() {
var detailSpan = document.querySelector("#detail");
if (typeof Worker != "undefined") {
if (typeof worker == "undefined") {
worker = new Worker("task.js");
}
worker.onmessage = function(event) {
message = event.data;
detailSpan.innerHTML = message;
};
} else {
message = "Sorry, your browser does not support web workers.";
detailSpan.innerHTML = message;
}
}
function terminate() {
worker.terminate();
worker = undefined;
}
</script>
<style type="text/css">
#status {
width: 600px;
height: 200px;
border:#CCDD66 1px solid;
margin:0 auto;
}
#btns {
margin-top: 20px;
text-align: center;
}
</style>
</head>
<body>
<div id="status">
<h3>status</h3>
<span id="detail"></span>
</div>
<div id="btns">
<button type="button" onclick="start()">Start</button> 
<button type="button" onclick="terminate()">Terminate</button>
</div>
</body>
</html>

task.js表示后台执行任务，代码如下：

var indexNumber = 0;

function timeCount() {
indexNumber += 1;
postMessage(indexNumber);
setTimeout("timeCount()", 500);
}

timeCount();

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