how find an element that does not exist in the first array with javascript?

Question

I have two arrays that look like this

first array

let arr1 = [
  'FS340089',
  'FS350089',
  'FS360089',
  'FS370089',
]

another array

let arr2 = [
  'FS340089',
  'FS350089',
  'FS360089',
  'FS370089',
  'FS380089',
]

I would like to get FS380089 at the output

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loop trough second array and search each item in first array. — vanowm, Jan 07 '23 at 18:17

score 1 · Accepted Answer · answered Jan 07 '23 at 18:19

1

Try this:

let arr3 = arr2.filter(x => arr1.indexOf(x) == -1);
console.log(arr3); // ["FS380089"]

It works by iterating through the second array and excluding values that are already in the first.

answered Jan 07 '23 at 18:19

CoderMuffin

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score 1 · Answer 2 · answered Jan 07 '23 at 18:19

You can use the find() & includes() methods:

let arr1 = [
  'FS340089',
  'FS350089',
  'FS360089',
  'FS370089',
]

let arr2 = [
  'FS340089',
  'FS350089',
  'FS360089',
  'FS370089',
  'FS380089'
]

let result = arr2.find(x => !arr1.includes(x))
console.log(result)

score 0 · Answer 3 · answered Jan 07 '23 at 18:31

This solution would resolve your problem by covering the case where the array length are different :

let arr1 = [
  'FS340089',
  'FS350089',
  'FS360089',
  'FS370089',
]

let arr2 = [
  'FS340089',
  'FS350089',
  'FS360089',
  'FS370089',
  'FS380089'
]

let result = arr2.length > arr1.length ? arr2.find(x => !arr1.includes(x)) :  arr1.find(x => !arr2.includes(x))
console.log(result)

how find an element that does not exist in the first array with javascript?

3 Answers3