Solution to Array pair sum problem in JavaScript

pairsum.js

var pairSum = (arr, k)=>{
  if(arr.length < 2){
    return
  }
  
  //  sets for tracting
  let seen = new Set();
  let output = new Set();
  
  for (let num of arr){
    let target = k - num;
    if(!seen.has(target)){
      seen.add(num)
    } else {
      let obj = [Math.min(num, target),Math.max(num, target)]
      output.add(obj)
      console.log(obj)
    }
  }
  return output.size
}

console.log(pairSum([1,3,2,2], 4))