Web Workers (執行緒應用)
- new Workers()
- new Shared Worker()
- 可以使用 navigator 物件
- 可以使用 XMLHttpRequest 物件
- 可以使用 WebSockets
- 此技術使得 Javascript 可以單獨被執行。
在 Web Worker 中，從網頁呼叫 Share Worker 會觸發
- onconnect
範例
<!DOCTYPE html>
<html>
<body>
<p>Count numbers: <output id="result"></output></p>
<button onclick="startWorker()">Start Worker</button>
<button onclick="stopWorker()">Stop Worker</button>
<p><strong>Note:</strong> Internet Explorer 9 and earlier versions do not support Web Workers.</p>
</body>
</html>
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 = "Sorry, your browser does not support Web Workers...";
}
}
function stopWorker() {
w.terminate(); // 停止執行緒
w = undefined;
}
Web Worker File
// demo_workers.js
var i = 0;
function timedCount() {
i = i + 1;
postMessage(i); // 發送訊息
setTimeout("timedCount()",500);
}
timedCount();
The important part of the code above is the postMessage() method - which is used to post a message back to the HTML page.
Note: Normally web workers are not used for such simple scripts, but for more CPU intensive tasks.