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Java Script Function

in java script a function is declared with keyword function followed by parentheses .Function may contain a parameter . The code of function executes when function is being called.

In JS function may be declared as following. In following example the function is being called on onLoad event . So it executes when we open the web page.


function MyFunction()
{
alert("This is Simple Function");
}

We can create n number of functions as per our requirements only called function will be executed. A function may also have parameter so when we call the function values as parameter have to be passed

JS function may also return the value for returning the value at the end of the function we have to give return statement.

<html>
<title>JS introduction</title>
<head>
<script>
function MyFunction()
{
alert("This is Simple Function");
}
</script>
</head>
<body onLoad="MyFunction()">
</body>
</html>

Output: This is simple function in alert pop up

In following example we have two functions we call MainFunction() on page load . MainFunction also calls another function SumFunction() which takes two values and return the sum after calculation. Main function receives the value and print it.

<html>
<title>JS introduction</title>
<head>
<script>
function SumFunction(n1,n2)
{
 var n=n1+n2;
 return n;
}
function MainFunction()
{
   var k=SumFunction(10,20);
   alert("The sum is"+k);
}
</script>
</head>
<body onLoad="MyFunction()">
</body>
</html>

Output: The sum is 30

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