When I push a field of a JavaScript array to another, the field also be pushed to the root array

Question

I have following code:

var oldArr = { "filed1" : "abcde", "filed2" : "fghij", "anArray" : [["aaa1","bbb1"],["aaa2","bbb2"],["aaa3","bbb3"]]};
var newArr = oldArr;
var isFirst = false;

               for(var i = 0; i < oldArr.anArray.length; i++){
                    var indexA = oldArr.anArray[i].indexOf("aaa1");
                    var indexB = oldArr.anArray[i].indexOf("bbb1");

                    if(indexA > -1 && indexB > -1){
                        if(i == 0){
                            isFirst = true;
                        }
                    }
                    else{
                        newArr.anArray.push(oldArr.anArrray[i]);
                    }
                }

Everytime I add an field to newArr.anArray it will also add the field to oldArr.anArray

Is my code wrong or is ther a dependence between newArr and oldArr?

Yes, there's a depedence, they are the same array, or object actually. — Teemu, Jun 23 '16 at 13:53
`var newArr = oldArr;` -> `newArr` gets a reference to `oldArr`, it is not a new object. — Arg0n, Jun 23 '16 at 13:53
`function makeArr() { return [ ... ]; }; var oldArr = makeArr(); var newArr = makeArr()` Make a function that returns the object, and make two copies of it by calling the function twice. And BTW `{ }` are objects and `[]` are arrays. — zeronone, Jun 23 '16 at 13:54
http://stackoverflow.com/questions/122102/what-is-the-most-efficient-way-to-clone-an-object/5344074#5344074 — Chris Hawkes, Jun 23 '16 at 13:56

score 0 · Accepted Answer · edited May 23 '17 at 11:58

0

You could to this:

var newArr = JSON.parse(JSON.stringify(oldArr));

As stated here (If the object does not contain functions)

edited May 23 '17 at 11:58

Community

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answered Jun 23 '16 at 13:56

Arg0n

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Still logging `Uncaught TypeError: Cannot read property '1' of undefined(…)` – guest271314 Jun 23 '16 at 14:02
Link to jsfiddle / plunkr please so i can test – Arg0n Jun 23 '16 at 14:03
1

You have three 'r' in anArrray: `newArr.anArray.push(oldArr.anArrray[i]);`. Use console of your browser to debug. – Arg0n Jun 23 '16 at 14:05
_"You have three 'r' in anArrray"_ `js` at OP contains same three "r" characters – guest271314 Jun 23 '16 at 14:16

score 0 · Answer 2 · answered Jun 24 '16 at 13:45

0

I solved the problem as I use a constructor for both objects. So there is no dependence between those objects.

answered Jun 24 '16 at 13:45

Johannes Scharf

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When I push a field of a JavaScript array to another, the field also be pushed to the root array

2 Answers2