Find the array index where a passed in number should be between (IE, [1,2,4] with a 3 passed in should = [1,2,3,4]

compareNumberToArrayItems.js

function getIndexToIns(arr, num) {
  let arrCopy = arr.sort(function(a, b){return a-b});
  let lastIndexOfLowerNum = 0;
  for(let i=0;i<arrCopy.length;i++){
    
    if(num>arrCopy[i]){
      lastIndexOfLowerNum = i + 1;
    } 
    if(num === arrCopy[i]){
      lastIndexOfLowerNum = i;
    }
  } 
  arrCopy.splice(lastIndexOfLowerNum,0,num);

  return arrCopy.indexOf(num);
}
 

getIndexToIns([5, 3, 20, 3], 5) //should return 2