extend.js

/**
 * Extend one object with the properties of any other object(s).
 * @param obj The object to extend.
 * @param args Additional arguments - the objects from which to copy properties.
 * @return The object which was extended.
 */
var extend = (function(){
    
    var
        slice = Array.prototype.slice,
        has = Object.prototype.hasOwnProperty;
        
    function extend( obj /*, args ... */ ) {
        var args = slice.call(arguments, 1);
        for (var i=0, l=args.length; i<l; i++) {
            var other = args[i];
            if (other) {
                for (var k in other) {
                    if (has.call(other, k)) {
                        obj[k] = other[k];
                    }
                }
            }
        }
        return obj;
    }
    
    return extend;
    
})();