Web worker

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The Web worker describes how the javaScript is executed in the background without affecting the user-interface scripts of the page.

The web worker is used effectively in multi core processors.

Types of web workers

  • Dedicated workers
  • Shared workers

Dedicated workers are accessible by the scripts from where they are loaded.

Shared workers are accessible by multiple scripts.

Sample code

The javaScript file using postMessage()

var num = prompt(“Enter a number”);

num = parseInt(num);

if (isNaN(num))

{

alert(“Enter a Number”);

}

else if (num == 0)

{

alert(“The number is zero”);

}

else if (num%2)

{

alert(“The number is odd”);

}

else

{

alert(“The number is even”);

}

postMessage(num);

The main program which calls postMessage() function

<!DOCTYPE html>

<html>

<head>

<title>web worker example<title>

</head>

<body>

<p>The number is even or odd <output id=”result”></output></p>

<script>

var worker = new worker(“evenorodd.js”);

worker.onmessage = function (event)

{

document.getElementById(“result”).textcontent = event.data;

};

</script>

</body>

</html>

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