Faster Algorithm for JavaScript function call within a function

Question

I have written a function and called another function inside but my tests show that it is not time optimized. How can I make the following code faster?

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Answer 1

Algorithmic optimization: create new array with cumulative sums from index 0 to every index

cumsum[0] = 0;
for (var i = 1; i <= arr.Length; i++) {
  cumsum[i] = cumsum[i-1] + arr[i-1]

Now you don't need to calculate sums for every range - just get difference

 sum for range (i..j) = cumsum[j+1] - cumsum[i];

in your terms:

    function sumAll(array1, myrange) {
            return cumsum[myrange[1]+1] - cumsum[myrange[0]];
    }

example:

arr = [1,2,3,4]
cumsum = [0,1,3,6,10]
sum for range 1..2 = 6 - 1 = 5

P.S. If your array might be updated, consider Fenwick tree data structure