Regex javascript allow only numbers, alphabets and underscore

Question

I'm using this code to prevent people from puting spaces between alphabets and numbers. I would lilke to modify the code so that only alphabets, letters and numbers can be typed.

This is what i'm doing:

 replace(/\sg, '') oin javascript

Can anyone help me as to how to costrucrt the regex expression so that only alphavets, nnumbers, underscore and no space can be keyed in the input box

Thanks

Have you tried to learn how to compose regular expressions?

zerkms
– zerkms

2013-08-26 01:33:19 +00:00
Commented Aug 26, 2013 at 1:33 — zerkms
– zerkms, Commented Aug 26, 2013 at 1:33
Please, take a look at the update here.

Ravi K Thapliyal
– Ravi K Thapliyal

2013-08-26 03:53:03 +00:00
Commented Aug 26, 2013 at 3:53 — Ravi K Thapliyal
– Ravi K Thapliyal, Commented Aug 26, 2013 at 3:53

Ravi K Thapliyal · Accepted Answer · 2013-08-26 03:53:51Z

4

Here's how you could do it with jQuery:

$(function() {
    $( '#username' ).on( 'keydown', function( e ) {
        if( !$( this ).data( "value" ) )
             $( this ).data( "value", this.value );
    });
    $( '#username' ).on( 'keyup', function( e ) {
        if (!/^[_0-9a-z]*$/i.test(this.value))
            this.value = $( this ).data( "value" );
        else
            $( this ).data( "value", null );
    });
});

SQL Fiddle Demo

edited Aug 26, 2013 at 3:53

answered Aug 26, 2013 at 2:47

Ravi K Thapliyal

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1 Comment

samrap Over a year ago

this is good, but if you hold the space bar or a character key down, you can get past it and it wont prevent characters from being entered...out of curiosity is there a way to prevent that?

p.s.w.g · Accepted Answer · 2013-08-26 01:33:21Z

2

Perhaps you want something like this:

var input = "f%o@o";
var output = input.replace(/\W/g, ''); // "foo"

This will remove any non-word character (a word character is a letter, number, or underscore) from the input string.

answered Aug 26, 2013 at 1:33

p.s.w.g

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4 Comments

Kwaasi Djin Over a year ago

I actually just want leters, numbers and unserscore to be in the input. So I guess the opposite

p.s.w.g Over a year ago

@KwaasiDjin That's what this will do. It will remove non-word characters.

Kwaasi Djin Over a year ago

yeah but this includes symbolds like @#$%^&*, however, i just want underscore letters and numbers

p.s.w.g Over a year ago

@KwaasiDjin Please see the example. "f%o@o".replace(/\W/g, '') becomes "foo".

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