deep copy in javascript

clone

function clone(obj) {
    // Handle the 3 simple types, and null or undefined
    if (null == obj || "object" != typeof obj) return obj;

    // Handle Date
    if (obj instanceof Date) {
        var copy = new Date();
        copy.setTime(obj.getTime());
        return copy;
    }

    // Handle Array
    if (obj instanceof Array) {
        var copy = [];
        for (var i = 0, var len = obj.length; i < len; ++i) {
            copy[i] = clone(obj[i]);
        }
        return copy;
    }

    // Handle Object
    if (obj instanceof Object) {
        var copy = {};
        for (var attr in obj) {
            if (obj.hasOwnProperty(attr)) copy[attr] = clone(obj[attr]);
        }
        return copy;
    }

    throw new Error("Unable to copy obj! Its type isn't supported.");
}

prototype.clone

Object.prototype.clone = function() {
  var copy = (this instanceof Array) ? [] : {};
  for (attr in this) {
    if (!obj.hasOwnProperty(attr)) continue;
    copy[attr] = (typeof this[i] == "object")?obj[attr].clone():obj[attr];
  } 
  return copy;
};


a = {k1:1, k2:2, k3:3};
b = a.clone();