nodejs find similarities in 2 arrays code example

Example 1: diff two arrays javascript

function diffArray(arr1, arr2) {
  return arr1
    .concat(arr2)
    .filter(item => !arr1.includes(item) || !arr2.includes(item));
}

Example 2: javascript get array difference

function arrayDiff (a1, a2) {
    var a = [], diff = [];
    for (var i = 0; i < a1.length; i++) {
        a[a1[i]] = true;
    }
    for (var i = 0; i < a2.length; i++) {
        if (a[a2[i]]) {
            delete a[a2[i]];
        } else {
            a[a2[i]] = true;
        }
    }
    for (var k in a) {
        diff.push(k);
    }
    return diff;
}
//usage:
console.log(arrayDiff(['red', 'white','green'], [ 'red','white', 'blue']));//["green", "blue"]