Compare one array with an 2 dimensional array in javascript

Question

a = [1,2,3];

b = [[1,2,3],[4,5,6]];

Why is that in javascript a== b[0] return false?

Thank you

Because JS compares objects not by values, but by references. If you used http://google.com with "javascript compare arrays" query you would find a lot of useful info — zerkms, Dec 10 '13 at 02:02
Consider that `[] == []` also returns `false`, because the arrays are different objects. There are plenty of ways to implement an array/object comparison function, you can use google for that. You could just use underscore and its [`_.isEqual()`](http://underscorejs.org/#isEqual) function. — sbking, Dec 10 '13 at 02:04
http://stackoverflow.com/questions/7837456/comparing-two-arrays-in-javascript. Really good answer. — Yogesh, Dec 10 '13 at 02:08

score 1 · Answer 1 · answered Dec 10 '13 at 02:09

In javascript objects are compared by references.

That said: a references to objects are compared, not the objects' contents.

Thus, One object {} will never be equal to another {} even though their contents are equal.

var a = {},
    b = {}; // not equal

Whereas if you create a variable by assigning another reference to it like:

var a = {},
    b = a; // equal

then both variables would hold the same reference and would be equal.

1 Answers1