Javascript checking only the first item of an array

Question

I have an array of arrays, i.e. [ [1,2], [1,3] ] and I want to check if is there any 1 as the first element of a subarray. It doesn't matter if it is a [1,2] or [1,3]. I'm interested only in the 1's existence. Sure I could use some loops to do this, but I wonder if is there an elegant "built-in" way to do this in js, something like:

arr.includes([1, _]) // returns true if is there any 1 as first element of an array

Nothing wrong with using a loop and breaking the loop if condition met. Built in methods are a bit easier to write but won't have greater efficiency — charlietfl
– charlietfl, Commented Aug 8, 2021 at 14:00

ulou · Accepted Answer · 2021-08-08 13:56:47Z

2

some is something you are looking for.

Code example:

const data = [[1, 3], [1, 5]] 

const res = data.some( ([a, _]) => a === 1 ) // less elegant alternative:
                                             // .some(e => e[0] === 1)

console.log(res)

answered Aug 8, 2021 at 13:56

ulou

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2 Comments

Paul Over a year ago

The , _ is pointless. You can just use [a]

ulou Over a year ago

Yes, that's true, but it better match OPs expectation.

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