Array referencing: adding an object to array of objects

Question

This is probably a very basic question - see a simple code:

var ar1=[];
var ar2=[];
ar1[0] = 'Constant';
ar1[1] = data.attr.const;
ar2.push(ar1);  //OK, ar2 contains one array of two correct elements

ar1[0] = 'R-squared';
ar1[1] = data.attr.rsq;
ar2.push(ar1);   // Not OK - ar2 contains 2 identical arrays

ar1[0] = 'R-sq. adjusted';
ar1[1] = data.attr.rsqadj;
ar2.push(ar1);   // Not OK - ar2 contains 3 identical arrays

The problem is that every time when it executes ar2.push(ar1), it overwrites all elements of ar2. After this code is executed, I get an obect with containing 3 identical arrays. How can I fix it?

Thanks

Because you are re-using the variable ar1, perhaps?

Sudipta Chatterjee
– Sudipta Chatterjee

2013-09-05 23:49:57 +00:00
Commented Sep 5, 2013 at 23:49 — Sudipta Chatterjee
– Sudipta Chatterjee, Commented Sep 5, 2013 at 23:49

elclanrs · Accepted Answer · 2013-09-05 23:50:00Z

6

Objects in JS are always references (unlike strings or numbers). Whenever you push you're referring to the same object that is already inside the array, you need to clone:

ar2.push(ar1.slice(0)); // clone ar1

answered Sep 5, 2013 at 23:50

elclanrs

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