Shallowly clones the object into the source object

@param {Object?} source The source object
@param {Object} obj The object to clone
@returns {Object} The source object
function shallowClone(source, obj) {
    if (arguments.length < 2) {
        obj = source;
        source = {};
    }

    for (var key in obj) {
        if (!obj.hasOwnProperty(key)) continue;
        source[key] = obj[key];
    }
    return source;
}