with this piece of jQuery I check if some fields are match or are not empty, but I get this error.

Uncaught TypeError: Cannot read property 'match' of undefined

Can anyone tell me what I am doing wrong here?

if ( width.match( /^d+$/ ) && height.match( /^d+$/ ) && type.length > 0 && color.length > 0 ) {

This is the full code:

if( $( #config ) ) {

        $( 'input, select' ).on( 'change', function(){

            var width   = $( #config-steps #width ).val();

            var height  = $( #config-steps #height ).val();

            var type    = $( #config-steps #type ).val();

            var color   = $( #config-steps #selected-color ).val();



            if ( width.match( /^d+$/ ) && height.match( /^d+$/ ) && type.length > 0 && color.length > 0 ) {

                $( #checkout-message ).show();



                // Change visible price 

                $( #change-price ).html( calculate_price().toFixed( 2 ) );



            } else {

                return false;

            }



        });

    }