How to check to see if there's an array within an array?

Question

The Problem

I want to test for the presence of an array inside of an array. For example, if my array is this:

let arr = ["all", ['>', 'PSF', 10]]

I want something like this to work:

let segment = ['>', 'PSF', 10]
arr.indexOf(segment) // would be equal to 1, in this case

What actually happens

arr.indexOf(segment) is currently -1, since I believe in JavaScript [] != [] due to the way it checks the array memory location.

At any rate, what would be the recommended way of testing to see if a specific array currently exists within an array? I also tried .includes(), but it seems to work the same way that indexOf works (so it failed).

Any help would be appreciated.

See stackoverflow.com/questions/7837456/… for how to compare two arrays for equal elements. — Barmar
– Barmar, Commented May 1, 2018 at 21:49

Hamza El Aoutar · Accepted Answer · 2018-05-01 21:55:18Z

3

You first need to create a function that compare 2 arrays, (the implementation will depend on your needs) , for example :

const compareArrays = (a1, a2) => Array.isArray(a1) && Array.isArray(a2) && a1.length === a2.length && a1.every((v, i) => v === a2[i])

You will need to define this function, because your array segment, may be more complicated, (i.e contains other arrays)

Then use some to check whether your original array contains the array (segment) :

arr.some(element => compareArrays(segment, element) )

Or findIndex, to get the index of the matching array (or -1 if no matching array exists)

arr.findIndex(element => compareArrays(segment, element) )

edited May 1, 2018 at 21:55

answered May 1, 2018 at 21:31

Hamza El Aoutar

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4 Comments

Thomas Over a year ago

careful, this will throw if any element (or segment) is null or undefined

yoursweater Over a year ago

How would I get the index value out of this though? I'd like to be able to see where the matching array is in the array i'm searching

Hamza El Aoutar Over a year ago

In this case use, findIndex instead of some

Hamza El Aoutar Over a year ago

@LGSon, I already mentionned this in my answer. (the compareArrays need to be updated depending on the arrays content)

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