My problem is simple I think, but I couldn't find a simple solution to it. Here is the example:

var obj1 = {
    m1:"a",
    m2:"b" 
};

var obj2 = {
    m:obj1
};


obj2.m.m1 = "c";


document.write(obj2.m.m1+"<br>"); //output: c

document.write(obj1.m1+"<br>"); // output: c ( I wanted to be a)

So.. what do I need to do to return "a" from obj1.m1 ?

Thanks in advance

My problem is simple I think, but I couldn't find a simple solution to it. Here is the example:

var obj1 = {
    m1:"a",
    m2:"b" 
};

var obj2 = {
    m:obj1
};


obj2.m.m1 = "c";


document.write(obj2.m.m1+"<br>"); //output: c

document.write(obj1.m1+"<br>"); // output: c ( I wanted to be a)

So.. what do I need to do to return "a" from obj1.m1 ?

Thanks in advance

• javascript
• variables
• scope

• possible duplicate of javascript how to create reference – Quentin Commented Apr 28, 2011 at 19:59
• @David Dorwad actually I'm looking for the opposite thing. How to pass objects as value and not as refference – Doua Beri Commented Apr 28, 2011 at 20:02

4 Answers 4

You need to set obj2.m to a clone of obj1, not obj1 itself. For instance:

function clone(obj) {
    var result = {};
    for (var key in obj) {
        result[key] = obj[key];
    }
    return result;
}

var obj2 = {
    m: clone(obj1)
};

obj2.m.m1 = "c";  // does not affect obj1.m1

This may be of use:

http://my.opera./GreyWyvern/blog/show.dml/1725165

obj1 and obj2.m point to the same object. You cannot have obj1.m1 != obj2.m.m1

What you can do is assign a copy of obj1 to obj2.m. See the link Will posted.

you need to clone it first.

Object.prototype.clone = function() {
  var newObj = (this instanceof Array) ? [] : {};
  for (i in this) {
    if (i == 'clone') continue;
    if (this[i] && typeof this[i] == "object") {
      newObj[i] = this[i].clone();
    } else newObj[i] = this[i]
  } return newObj;
};

var obj1={    m1:"a",    m2:"b" };
var obj2={    m: {}};
obj2.m = obj1.clone();
obj2.m.m1="c";
document.write(obj2.m.m1+"<br>"); 
document.write(obj1.m1+"<br>");