ECMAScript5 deep copy of object and arrays

Question

I'd hope to find an example code to do a deep copying of objects in ECMAScript5.

The copying should be able to clone

Nested objects
Nested arrays
Nested objects in arrays (clone each array item individually)

Note: jQuery.extend() does not seem to handle case 3). Also, I'd hope to do this in clean ECMAScript. Quick googling did not bring up any worthy implementations.

Deep copying is a non trivial problem, I recommend you change your algorithm so it works with a shallow copy — Raynos, Nov 29 '11 at 02:47
Currently I am doing it with jQuery.extend() and manually cleaning up the mess afterwards — Mikko Ohtamaa, Nov 29 '11 at 12:09

neaumusic · Answer 1 · 2015-03-02T22:21:38.637

1

if you want a one-liner (removes object refs by iterating through referenced objects to retrieve primitives, concats one large string, then parses the string into a new object with it's own primitive leaf nodes)

JSON.parse(JSON.stringify(obj))

or if you need to perform many copies

function deepCopy(o) {
    var copy = o,k;

    if (o && typeof o === 'object') {
        copy = Object.prototype.toString.call(o) === '[object Array]' ? [] : {};
        for (k in o) {
            copy[k] = deepCopy(o[k]);
        }
    }

    return copy;
}

performance comparison

edited Mar 02 '15 at 22:21

answered Feb 26 '15 at 20:37

neaumusic

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What do you mean? This does perform a deep copy. Its not specifically ECMAScript5 but neither is jQuery right? – neaumusic Feb 27 '15 at 07:34
Sorry! What I meant to say is please explain what's the code doing? – Saifur Feb 27 '15 at 12:51

score 1 · Accepted Answer · answered Feb 25 '12 at 12:01

1

I finally settled to jQuery.extend() as I couldn't find other good implementations

http://api.jquery.com/jQuery.extend/

answered Feb 25 '12 at 12:01

Mikko Ohtamaa

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score 0 · Answer 3 · edited May 23 '17 at 12:20

Use an emulation of the toSource method to copy the object:

    <script type="text/javascript">
    Object.prototype.getSource = function() {
      var output = [], temp;
      for (var i in this) {
          if (this.hasOwnProperty(i)) {
              temp = i + ":";
              switch (typeof this[i]) {
                  case "object" :
                      temp += this[i].getSource();
                      break;
                  case "string" :
                      temp += "\"" + this[i] + "\"";    // add in some code to escape quotes
                      break;
                  default :
                      temp += this[i];
              }
              output.push(temp);
          }
      }
      return "{" + output.join() + "}";
      }
      var baz = {"alpha":{"beta":{"charlie": ["delta","epsilon",{"omega":"zeta"}]}}};
      !!Object.prototype.toSource ? alert((baz).toSource() ) : alert((baz).getSource() );
    </script>

A start, but isn't this little fragile.. possible infinite loop with cyclic references? — Mikko Ohtamaa, Feb 29 '12 at 08:37
[Contact the developer](http://stackoverflow.com/users/9021/nickf) of this solution for help with robustness. — Paul Sweatte, Feb 29 '12 at 18:31

ECMAScript5 deep copy of object and arrays

3 Answers3

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