How to use varioable in reguler expression???

prajwala · 10-04-2012, 12:05 PM

I have called a function with passing 2 arguments in it.i is for id and other is for number.

I want to use that number in reguler expression.

Please find below code:

<html>
<head>
<script type="text/javascript">
function checkNumber(id,num){
var elementTxt=document.getElementById(id);
var a=parseInt(num);
var re5digit='/^\d{'+num+'}$/'; //regular expression defining a 5 digit number

if(elementTxt.value!=null || elementTxt.value!=""){
if (elementTxt.value.search(re5digit)==-1 ) //if match failed
{
alert("Please enter a valid 5 digit number inside form");
//return false;
}
}
}
</script>
</head>
<body>
<input type="text" id='txt'/>
<input type="button" value="ok" onclick="checkNumber('txt',5)"/>
</body>
</html>

devnull69 · 10-04-2012, 01:18 PM

Your variable re5digit is of type "string" and not of type "RegExp".

Code:

var re5digit = new RegExp('/^\d{'+num+'}$/');

Philip M · 10-04-2012, 01:43 PM

Regular expressions can be handy for a lot of things, but for simpler tasks they are not the most efficient way. I would suggest determining if the field is not a number and is of a certain length:-

Code:

<html>
<head>

<script type="text/javascript">

function checkNumber(id,num) {
// num is a number already so no need for parseInt(), which in any case ought to specify the radix
var elementTxt = Number(document.getElementById(id).value);
if ((isNaN(elementTxt))  || (elementTxt.toString().length != num)) {
alert ("Please enter a valid " + num + "-digit number inside form");
document.getElementById(id).value = "";  // clear the field
return false;
}
}

</script>

</head>
<body>
<input type="text" id='txt' size = "5" maxlength = "5"/>
<input type="button" value="Check It" onclick="checkNumber('txt',5)"/>

</body>
</html>

The value of a form field can never be null. Only "" (blank).

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prajwala · 10-04-2012, 01:58 PM

Hey thanks all.
It worked