JS Functions



Functions in JavaScript

  • JavaScript function is collection of JavaScript Statements , that are grouped together and enclosed within Opening Curly and Closing Curly braces.
  • JavaScript function can be called using different methods.
  • JavaScript Function Can return a value.

JavaScript Function Can be placed –

  • Inside Head Section
  • Inside Body Section
  • Inside External File having (.js) extension.

Note :

JavaScript Function must be loaded before calling it , so we must write JavaScript function inside <head> and </head> section

JavaScript Function can be called by –

  • Automatically when Page gets loaded completely
  • Can be invoked by any JavaScript Event.

How to declare a function ?

function FunctionName(var1,var2,...,varX)
{
some code
}

Explanation :

  1. function keyword is used to write definition of function.
  2. Parameters can be passed to JS function separated by comma.
  3. Code included inside “Opening Curly” and “Closing Curly“.
  4. return” statement is used to return value from function.

Live Example :

<html>
<head>

<script type="text/javascript">
function print()
{
alert("Hello World!");
}
</script>

</head>

<body>

<form>
<input type="button"
       value="Call Function"
       onclick="print()" />
</form>

</body>
</html>

Output :

Download JS Function Example : Click Here