How to create a copy of a JSON Object Array

Question

I have been trying to figure out how to make a copy of a JSON object array that can be modified without changing the original. I do see a lot of discussion regarding objects being passed as a reference by default, but I don't understand how to avoid this default behavior.

The example jQuery below is not real code, but I think it illustrates what I am trying to accomplish. Can anyone help me understand how to code the following example so that _copy can be modified with _master being left unmodified?

// Master - should never get modified
_master = [ 
    Object { id=0, name="Charlie", city="Memphis", state="TN" },
    Object { id=1, name="Steve", city="Chicago", state="IL" } 
];

// Copy of Master that can be modified
_copy = _master;

// Modify _copy only - leave _master unmodified
_copy[0].name = "Charles";

JSON has nothing to do with what you're attempting. Those are just object literals. — Brad
– Brad, Commented Jan 17, 2015 at 21:28
possible duplicate of What is the most efficient way to clone an object? — Brad
– Brad, Commented Jan 17, 2015 at 21:29

David Xu · Accepted Answer · 2015-01-17 21:34:01Z

3

You can use this:

var copyArray = JSON.parse(JSON.stringify(someArray));

answered Jan 17, 2015 at 21:34

David Xu

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1 Comment

rwkiii Over a year ago

Your answer is identical to chiliNUT. I wish I could mark both of you as answers. +1 for your help. Thank you.

chiliNUT · Accepted Answer · 2015-01-17 21:40:14Z

2

_copy=JSON.parse (JSON.stringify (_master));

is a quick way to do it. The encode converts _master to a string representation of the variable, and the parse consumes it and turns it back into an array.

Any referential/memory connection is severed once the variable is converted to a string.

edited Jan 17, 2015 at 21:40

answered Jan 17, 2015 at 21:33

chiliNUT

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