What does comparing 2 Array mean in Javascript? [duplicate]

Question

Inside my node.js REPL I create 4 arrays : a = [1,2,3], b=[], c=[4,5], d=null ( ok d is not an array but you get my point)

I compare them directly this way :

> b = []
[]
> a > b
true
> b > a
false
> a > c
false
> c > a 
true
> c > b
true
> b > c
false
> d > a
false
> a > d
false

What are these expressions actually evaluating? I see that it's clearly not the length of the arrays. Otherwise c > a would have been false.

Can somebody please help me understand!

You need to learn a lot of javascript's implicit conversions (i personally prefer explicit ones, where comparing arrays like that just throws, but it is what it is), and use them one after another. — ASDFGerte
– ASDFGerte, Commented Sep 23, 2021 at 18:40
The short version is, JavaScript is casting the array to some other type and using that type's comparator for the operator> evaluation. Since these results don't have any valuable semantic meaning, it's basically a pointless operation and you should create your own routine for comparing arrays if you need that functionality. There isn't much point in further stressing why JavaScript chooses to implement things this way, as there are many other examples of weird JavaScript behavior. — h0r53
– h0r53, Commented Sep 23, 2021 at 18:49

maybebot · Accepted Answer · 2021-09-23 18:57:00Z

0

The arrays get converted to strings first (including the commas).

[1, 2, -3] for instance becomes the string '1,2,-3'

Then the strings get compared in an "alphabetical" order (based on their character codes).

It is not a very intuitive way of accomplishing comparisons, and should be avoided.

answered Sep 23, 2021 at 18:51

maybebot

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