JSFiddle - React, Tailwind, and code Playground

JavaScript

const array1 = [2,1,3,5,2,1,3,5];
    const array2 = [4,3,2,6,7,4,3,2,6,7];
    
    function diff(arr1, arr2) {
        let dontAddDuplicates = true;
        let a1hash = {};
        let a2hash = {};
        let a1 = [];
        let a2 = [];
        let i = 0;
        let j = 0;
        for (let i = 0; i < arr1.length; i++) {
           a1hash[arr1[i]] = 0;
        }
        for (let i = 0; i < arr2.length; i++) {
           a2hash[arr2[i]] = 0;
        }
        for (let i = 0; i < arr1.length; i++) {
           if (!a2hash.hasOwnProperty(arr1[i])) {
              if (!dontAddDuplicates || a1hash[arr1[i]] == 0) {
                 a1hash[arr1[i]] = 1;
                 a1.push(arr1[i]);
              }
           }
        }
        for (let i = 0; i < arr2.length; i++) {
           if (!a1hash.hasOwnProperty(arr2[i])) {
              if (!dontAddDuplicates || a2hash[arr2[i]] == 0) {
                 a2hash[arr2[i]] = 1;
                 a2.push(arr2[i]);
              }
           }
        }
        return [a1, a2];
    }

    console.log(diff(array1, array2));