将对象的所有键转换为小写的最佳方法(最有效)是什么?

我想出了

function keysToLowerCase (obj) {
  var keys = Object.keys(obj);
  var n = keys.length;
  while (n--) {
    var key = keys[n]; // "cache" it, for less lookups to the array
    if (key !== key.toLowerCase()) { // might already be in its lower case version
        obj[key.toLowerCase()] = obj[key] // swap the value to a new lower case key
        delete obj[key] // delete the old key
    }
  }
  return (obj);
}

但我不确定 v8 会如何处理它，例如，它真的会删除其他键还是只会删除引用而垃圾收集器稍后会咬我?

var key, keys = Object.keys(obj);
var n = keys.length;
var newobj={}
while (n--) {
  key = keys[n];
  newobj[key.toLowerCase()] = obj[key];
}