jQuery Forum

I am reading the source of jQuery UI,

$.widget = function( name, base, prototype ) {
    var namespace = name.split( "." )[ 0 ],
        fullName;
    name = name.split( "." )[ 1 ];
    fullName = namespace + "-" + name;

    ///parameter shifting
    if ( !prototype ) {
        prototype = base;
        base = $.Widget;
    }
...}

The semantics here is to support optional parameter base,
you can do $.widget(name, prototype) or $.widget(name, base, prototype)
the idea is good, but what is odd is that the position of optional parameter is in the middle of function, but not the last one. We should support calls like
$.widget(name, prototype) or $.widget(name, prototype, base)

$.widget = function( name, prototype, base) {
//..
  if (!base) {
   base = $.Widget;
}
//..
}

But since this interface has been used already, refactory is almost impossible, as it change the semantics and will break other code. My idea is that optional parameter should be the last one, is this good or bad?
Thanks

I know that every language has its own culture, the culture of JavaScript  is definitely unique. I am a big fan of  jQuery, but I have mixed feeling in the implementation of jQuery core. The passed in parameters get reused and overloaded for semantics in many places, is it part of javascript culture. I know this might help to improve performance, but I don't know the actual performance gain, but the cost of maintenance  will definitely increase. I have changed dataAttr function in data module of jQuery core, and it is for my personal understanding. The code passed the unit test in firefox 3.6. Do you think it is better or worse? Thanks

function tryGetDataFromHtml5DataAttr(elem, key, data) {
    //if data is has value already
    //or elem is not element node
    if (data !== undefined || elem.nodeType !== 1) {
        return data;
    }
    // If nothing was found internally, try to fetch any
    // data from the HTML5 data-* attribute
    var attributeValue = elem.getAttribute("data-" + key);
    if (typeof attributeValue !== "string") {
        return undefined;
    }

    var setData;
    try {
        if (attributeValue === "true") {
            setData = true;
        } else if (attributeValue === "false") {
            setData = false;
        } else if (attributeValue === "null") {
            setData = null;
        } else if (!jQuery.isNaN(attributeValue)) {
            setData = parseFloat(attributeValue);
        } else if (rbrace.test(attributeValue)) {
            setData = jQuery.parseJSON(attributeValue);
        } else {
            setData = attributeValue;
        }
    } catch(e) {
        setData = attributeValue;
    }

    // Make sure we set the data so it isn't changed later
    jQuery.data(elem, key, setData);
    return setData;
}