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Thursday, February 27, 2014

JavaScript Functions example



In this post we will discuss about JavaScript functions, how to create as well as how we can call a function. Also you can check my previous posts on:

- Constraints in SQL Server 2008

- Generics tutorial in C#.Net

- Creating a New ASP.NET 4 Web Site

A function is a block of statements that can performs some task as well it can also return some value. A function is independent of your program and not executed until called.

Functions must be declared before they can be used. Normally functions are placed in the <head> tag of the HTML document to ensure that they are defined before used.

In JavaScript, we can define a function by using the function keyword. Also a function can take some parameters.

Syntax:

function function_name ()
{
statement 1;
statement 2;
}

function function_name (parameter1, parameter 2)
{
statement 1;
statement 2;
}

Example:
Here in this example, we write a method inside the <head> </head> tag,  which will give an alert message. And in a hyperlink we are calling that method in the body like below:

<head runat="server">
    <title>JavaScript Function Example</title>
    <script language="JavaScript" type="text/javascript">
        function HelloWord() {
            alert('Hello World !!!')
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <a href="javascript:HelloWord()">Click here </a>
    </div>
    </form>
</body>

see fig below:

simiarly if you want to call the javascript methos in a asp button control, then you can call the method in the OnClientClick event like below:

<asp:Button ID="btnCall" runat="server" Text="Call JavaScript Function" OnClientClick="HelloWord();" />



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