looping two arrays to get unique elements from one array - google-apps-script

Question

I have
arr1 = [ 'Account2', 'Account4', 'Account4', 'Account5' ]
and arr2 = [ 'Account2', 'Account4', 'Account7' ]
I want to loop through both the arrays and get a new array with only the elements which are present in arr1 but not present in arr2
so the new array should have
arr3 = ['Account5']
I tried this
for (var i = 0; i < arr1.length; i++) {
for (var j = 0; j < arr2.length; j++) {
if (arr1[i] != arr2[j]) {
arr3.push(arr1[i]);
}
}
}
console.log("arr3", arr3);

Answer 1

Your code is not correct because it will push every element of arr1 that is not equal to any element of arr2, which will result in duplicates and unwanted values.
One possible way is to use a flag variable to check if an element of arr1 is present in arr2 or not, and only push it to arr3 if it is not present. For example:
var arr1 = [ 'Account2', 'Account4', 'Account4', 'Account5' ];
var arr2 = [ 'Account2', 'Account4', 'Account7' ];
var arr3 = [];
for (var i = 0; i < arr1.length; i++) {
var flag = false; // assume the element is not present in arr2
for (var j = 0; j < arr2.length; j++) {
if (arr1[i] == arr2[j]) {
flag = true; // found the element in arr2, set the flag to true
break; // no need to continue the inner loop
}
}
if (!flag) { // if the flag is still false, it means the element is not present in arr2
arr3.push(arr1[i]); // push it to arr3
}
}
console.log("arr3", arr3); // ["Account5"]