Question

I read that the which parameter in all jQuery events are normalized ( specified here ).
However, I was trying to figure out where in the source ( of jQuery ), this normalization is achieved. I’m interested in figuring out how it is done. Anybody have an idea? Could you either point me in the right direction or post an explanation here ?

Answer 1

Check the code of keyHooks and mouseHooks:

keyHooks: {
    props: "char charCode key keyCode".split(" "),
    filter: function( event, original ) {

        // Add which for key events
        if ( event.which == null ) {
            event.which = original.charCode != null ? original.charCode : original.keyCode;
        }

        return event;
    }
},

mouseHooks: {
    props: "button buttons clientX clientY fromElement offsetX offsetY pageX pageY screenX screenY toElement".split(" "),
    filter: function( event, original ) {
        var eventDoc, doc, body,
            button = original.button,
            fromElement = original.fromElement;

        // Calculate pageX/Y if missing and clientX/Y available
        if ( event.pageX == null && original.clientX != null ) {
            eventDoc = event.target.ownerDocument || document;
            doc = eventDoc.documentElement;
            body = eventDoc.body;

            event.pageX = original.clientX + ( doc && doc.scrollLeft || body && body.scrollLeft || 0 ) - ( doc && doc.clientLeft || body && body.clientLeft || 0 );
            event.pageY = original.clientY + ( doc && doc.scrollTop  || body && body.scrollTop  || 0 ) - ( doc && doc.clientTop  || body && body.clientTop  || 0 );
        }

        // Add relatedTarget, if necessary
        if ( !event.relatedTarget && fromElement ) {
            event.relatedTarget = fromElement === event.target ? original.toElement : fromElement;
        }

        // Add which for click: 1 === left; 2 === middle; 3 === right
        // Note: button is not normalized, so don't use it
        if ( !event.which && button !== undefined ) {
            event.which = ( button & 1 ? 1 : ( button & 2 ? 3 : ( button & 4 ? 2 : 0 ) ) );
        }

        return event;
    }
},