How to add elements of an array that is a return of another function in JavaScript?

The error is in the index within the loop for of the array that is exceeding the number of elements:

            aqui está o erro
                  ↓
for(var i = 0; i <= numbers.length; i++){
    soma += numbers[i];
}

The correct one would be:

for(var i = 0; i < numbers.length; i++){
    soma += numbers[i];
}

As a beginner, I'll list the array's indexes:

numbers[0] = 1;
numbers[1] = 2;
numbers[2] = 3;
numbers[3] = 4;
numbers[4] = 5;
numbers[5] = 6;
numbers[6] = 7;
numbers[7] = 8;
numbers[8] = 9;
numbers[9] = 10;

The index of arrays always starts with 0 , so to go through the entire array, you must specify in the for loop that the variable ( i=0 ) is less than the length size of the array. / p>

In this case, the array has 10 elements, but the for loop must end in 9 because it starts with 0 , that is, 0 to 9 is 10 loops.