pairs of array that sum to X, O(n)

pairs.js

let pairs = (arr: number[], s: number): number[][] => {
  let cache = {};
  let res = [];
  for (let i of arr) {
    if (!cache[i]) {
      cache[i] = true;
    }
    let snd = s - i;
    if (cache[snd]) {
      res.push([i, snd]);
    }
  }
  return res;
};


let res = pairs([1, 2, 4, 3, 0, 5, 9, 6, 8, 7].sort(), 7);

console.log(res);