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 google.com with "javascript compare arrays" query you would find a lot of useful info — zerkms
– zerkms, Commented Dec 10, 2013 at 2:02
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() function. — sbking
– sbking, Commented Dec 10, 2013 at 2:04
stackoverflow.com/questions/7837456/…. Really good answer. — Yogesh
– Yogesh, Commented Dec 10, 2013 at 2:08

zerkms · Accepted Answer · 2013-12-10 02:09:52Z

1

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.

answered Dec 10, 2013 at 2:09

zerkms

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