short circuit Array.reduce in Javascript

Question

A toy example of a pattern I am trying to solve elegantly. In the below algorithm, I would like to immediately return 0 from reduce when I find an element with a value of 0 without visiting the remaining elements.

let factors = [2,3,6,0,9,4,4,4];
function product(arr) {
    return arr.reduce((acc, elem) => (acc * elem), 1);
}

Is there some way to break out of the reduce iteration?

write your custom reduce function if you have specific requirements. — VivekN, Jun 05 '17 at 20:31
reduce function in general would iterate over the entire array. — VivekN, Jun 05 '17 at 20:32
Why not just `return ~arr.indexOf(0) ? 0 : arr.reduce(/* ... */);` — Emissary, Jun 05 '17 at 20:35
@Emissary, that would work for the above example but not my application of this pattern. — Doug Coburn, Jun 05 '17 at 20:39
You are right Xufux, just realized that right now. your answer is right here. you need to make your own reduce function. if you want to use it functionally https://stackoverflow.com/questions/36144406/how-to-break-on-reduce-method — Rick, Jun 05 '17 at 20:47

Rick · Answer 1 · 2017-06-08T00:21:35.040

-2

You can short circuit reduce by mutating the original array.

let factors = [2, 3, 6, 0, 9, 4, 4, 4];

function product(arr) {
  return arr.reduce((acc, elem, i, array) => (array[i] === 0 ? (arr.length = i, elem) : (acc * elem)), 1);

}
console.log(product(factors))

edited Jun 08 '17 at 00:21

answered Jun 05 '17 at 20:43

Rick

1,035
10
18

short circuit Array.reduce in Javascript

1 Answers1