JSFiddle - React, Tailwind, and code Playground

JavaScript

var arr1 = [1,9,3,5,4,8,2,6,3,4]
    var arr2 = [5,2,4,8,2,6,4]
    var arr3 = [];
    var arr1length = arr1.length;
    var arra2length = arr2.length;
    var finalResult;
   for(var i = 0; i < arr1length; ++i){
        for(var j=0;j<arra2length;j++) {
            if((arr1[i] == arr2[j] && arr1[i-1] == arr2[j-1]) || (arr1[i] == arr2[j] && arr1[i+1] == arr2[j+1])) {
                arr3.push(arr1[i]);
                
            }
            else
            {
                finalResult = arr3.toString();
            }
        }
    }

    alert(finalResult);