Check If Equal Value in Multiple Arrays [duplicate]

Question

I have 3 arrays named "localCodes", "standardCodes", and "specialCodes". I am trying to confirm if there are any distinct values that appear in all 3 arrays.

What is the most efficient way of going about this?

EDIT:

Below is the code I was playing with, I just feel like there is a simpler way here that I am not getting

Example data set:

localCodes = [1,2,3,4]
standardCodes = [10,2,11,44]
specialCodes = [99,98,89,2]

With that set I would want to return true because 2 is found in each of the 3 arrays.

var longest = localCodes
var longFlag = 'local'
if(standardCodes.length > longest.length){
    longest = standardCodes
    longFlag = 'standard'
}
if(specialCodes.length > longest.length){
    longest = specialCodes
    longFlag = 'special'
}

for(l=0; l<longest.length; l++){
    if(longFlag == 'local'){
        //code here
    }
    if(longFlag == 'standard'){
        //code here
    }
    if(longFlag == 'special'){
        //code here
    }
}

Are you trying to check if a specific value exits in all three? Or are you trying to find where all three overlap? — VLAZ
– VLAZ, Commented Nov 13, 2024 at 18:44
@VLAZ if ANY value exists in all 3. Once I know that there is at least 1 value that is in all 3 i'd be all set — M. Pollino
– M. Pollino, Commented Nov 13, 2024 at 18:45

Mr. Polywhirl · Accepted Answer · 2024-11-13 18:53:52Z

You can map all the lists to a collection of sets and then reduce them by calling intersection.

const
  localCodes    = [ 1,  2,  3,  4],
  standardCodes = [10,  2, 11, 44],
  specialCodes  = [99, 98, 89,  2];
  
const getIntersectingValues = (...arr) => [...arr
  .map(arr => new Set(arr))
  .reduce((acc, cur) => acc.intersection(cur))];
  
const sharedValues = getIntersectingValues(
  localCodes,
  standardCodes,
  specialCodes
);

console.log(sharedValues); // [2]

If you just want a boolean, you can check the resulting size of the reduced intersection:

const
  localCodes    = [ 1,  2,  3,  4],
  standardCodes = [10,  2, 11, 44],
  specialCodes  = [99, 98, 89,  2];
  
const hasIntersectingValues = (...arr) => arr
  .map(arr => new Set(arr))
  .reduce((acc, cur) => acc.intersection(cur))
  .size > 0;
  
const hasIntersection = hasIntersectingValues(
  localCodes,
  standardCodes,
  specialCodes
);

console.log(hasIntersection); // true

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