What's the best way (most efficient) to turn all the keys of an object to lower case?

Question

I\'ve come up with

function keysToLowerCase (obj) {
  var keys = Object.keys(obj);
  var n = keys.length;
  while (n--) {
    var key = keys[n]; // \"cache\"         


        

Answer 1

Consider lowering case just once, storing it in a lowKey var:

function keysToLowerCase (obj) {
  var keys = Object.keys(obj);
  var n = keys.length;
  var lowKey;
  while (n--) {
    var key = keys[n];
    if (key === (lowKey = key.toLowerCase()))
    continue

    obj[lowKey] = obj[key]
    delete obj[key]

  }
  return (obj);
}