How can I use reduce to calculate the intersection of multiple arrays?

Question

Example:

myArray = [[1,2,3,4],
           [2,3,4,5], 
           [3,4,5,6]
          ];

Expected output:

newArray = [3,4]

How do I generate a new array with the values present in all 3 arrays?

Answer 1

While reducing, return an intersection of the accumulator with the current sub-array being iterated over:

 const myArray = [[1,2,3,4], [2,3,4,5], [3,4,5,6]]; const intersection = myArray.reduce((a, arr) => ( a.filter(num => arr.includes(num)) )); console.log(intersection); 

Answer 2

You can use .filter() to extract the matching values:

 let myArray = [[1, 2, 3, 4], [2, 3, 4, 5], [3, 4, 5, 6]]; let intersect = ([f, ...r]) => f.filter(v => r.every(a => a.includes(v))); console.log(intersect(myArray));