Adding and modifying an element in a javascript array

Question

Good day. Array:

var cap = [ ['a', 'b', 'c', 1], ['a', 'q', 'c', 0] ];

It is necessary to add an element equal to the last current to the end of the array, while changing the current value of 0 to 1, i.e. get the view:

  cap = [ ['a', 'b', 'c', 1], ['a', 'q', 'c', 1], ['a', 'q', 'c', 0] ];

I do this:

 cap.push(cap[cap.length-1]); cap[cap.length-1][3]= 1;

but I get all the units at the end. Correct, please. Thank.

PS

The first line changed to:

 cap[cap.length] = cap[cap.length-1];

same result instead

  cap = [ ['a', 'b', 'c', 1], ['a', 'q', 'c', 1], ['a', 'q', 'c', 0] ];

I get:

  cap = [ ['a', 'b', 'c', 1], ['a', 'q', 'c', 1], ['a', 'q', 'c', 1] ];

UPD_2 I think the problem is that I insert the element not as an array, I did this:

 cap[cap.length] = '['+cap[cap.length-1]+']';

also some kind of curvature, but with numbers 0 and 1 here is already ok ...

So why do you add 1 to the last element, you need 0 cap [cap.length-1] [3] = 1;
When I put 0, I get an alert: cap = a, b, c, 1, a, q, c, 0, a, q, c, 0

Vlad Churakov Vlad Churakov 201 one one · Accepted Answer · 2015-08-27T20:08:09

In the cap array, the last two elements are the same object (array):

 cap[ cap.length - 1 ] === [ cap.length - 2 ] => true

need to clone an array:

 cap[ cap.length ] = cap[ cap.length - 1 ].slice(); cap[ cap.length - 2 ][ 3 ] = 1;

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