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
<html>
<head>
<script type="text/javascript"></script>
</head>
<body>
<form name="iForm">
<input type="text" name="iText" />
<button onclick="validateInput();">Click Me</button>
</form>
</body>
</html>
and between the script tags we put our JavaScript code the will get the job done
function validateInput()
{
var reg = /^\d{6}$/
if(document.iForm.iText.value.search(reg)==-1)
{
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})+$/
if(document.iForm.iText.value.search(reg)==-1)
{
alert("Wrong Email.....Please Enter Valid Email !!!!")
}
}
hope you enjoyed this simple tutorial :)