How to find the sum of an array of numbers

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This’d be exactly the job for reduce.

If you’re using ECMAScript 2015 (aka ECMAScript 6):

const sum = [1, 2, 3].reduce((partialSum, a) => partialSum + a, 0);
console.log(sum); // 6

For older JS:

const sum = [1, 2, 3].reduce(add, 0); // with initial value to avoid when the array is empty

function add(accumulator, a) {
  return accumulator + a;
}

console.log(sum); // 6

Isn’t that pretty? 🙂

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