Question

Looking for something that if my select with an id of contentPageID gets changed then it clears the value of the input with an id of itemURL and vice-versa. If a value is put for the input text then the val of the select turns to 0.

Answer 1

Here’s one more way:

$('#contentPageID, #itemURL').change ( function () {

    if ( $(this).is ('select') ) {
        $('#itemURL').val ("");
    }
    else {
        //--- Note that jQuery intelligently sets <select>s.
        $('#contentPageID').val (0);
    }
} );

See it in action.