Validating user input in JavaScript

Many developers may face a big problem while dealing with JavaScript; it’s the problem of validating user input using REGULAR EXPRESSIONS

Here are simple steps to do so:

-First what is a regular expression?!

It’s a tool for performing pattern matches and it has to categories

1-literal syntax , it’s something like that

var reg = /pattern/<br />

2-Dynamic regular expression that can be done using the RegExp() constructor , it’s something like that

var reg = new RegExp("pattern") ;<br />

after we have got a regular expression we can use it any where

and here’s an example that may be helpful

-In this example we insure that the user enters 6 digits.

first i’ll construct an html form like that

		<script type="text/javascript"></script>

		<form name="iForm">
			<input type="text" name="iText" />
			<button onclick="validateInput();">Click Me</button>

and between the script tags we put our JavaScript code the will get the job done

function validateInput()
	var reg = /^\d{6}$/
		alert("Wrong input.....Please Enter Valid input !!!!")

Here i’ll reveal some mysterious about the previous expression

^ this means that it will start comparing from the first digit d{6} means that it will do comparing for 6 digits $ means that it must be 6 digits till the end of the input(actually $ means the end of the input)

here’s another trick if you want to validate email input from the user

we can do this with this function

function validateInput()
	var reg = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/
		alert("Wrong Email.....Please Enter Valid Email !!!!")

hope you enjoyed this simple tutorial :)