Chapter: Web Technology : JavaScript (JS)

Javascript Functions

A function will be executed by an event or by a call to the function.

JAVASCRIPT FUNCTIONS

A function will be executed by an event or by a call to the function.

JavaScript Functions

To keep the browser from executing a script when the page loads, you can put your script into a function.A function contains code that will be executed by an event or by a call to the function.You may call a function from anywhere within a page (or even from other pages if the function is embedded in an external .js file).Functions can be defined both in the <head> and in the <body> section of a document. However, to assure that a function is read/loaded by the browser before it is called, it could be wise to put functions in the <head> section.

How to Define a Function

Syntax

function functionname(var1,var2,...,varX)

{

some code

}

The parameters var1, var2, etc. are variables or values passed into the function. The { and the } defines the start and end of the function.

Note: A function with no parameters must include the parentheses () after the function name.

Note: Do not forget about the importance of capitals in JavaScript! The word function must be written in lowercase letters, otherwise a JavaScript error occurs! Also note that you must call a function with the exact same capitals as in the function name.

JavaScript Function Example

<html>

<head>

<script

type="text/javascript"> function displaymessage()

{

alert("Hello World!");

}

</script>

</head>

<body>

The return Statement

The return statement is used to specify the value that is returned from the function.So, functions that are going to return a value must use the return statement.The example below returns the product of two numbers (a and b):

Ex:

<html>

<head>

<script

type="text/javascript"> function product(a,b)

{ return a*b;

}

</script>

</head>

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Web Technology : JavaScript (JS) : Javascript Functions |