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

Answer 1

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

Answer 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.