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

Here's my recursive version based on one of the above examples.

//updated function
var lowerObjKeys = function(obj) {
  Object.keys(obj).forEach(function(key) {
    var k = key.toLowerCase();
    if (k != key) {
      var v = obj[key]
      obj[k] = v;
      delete obj[key];

      if (typeof v == 'object') {
        lowerObjKeys(v);
      }
    }
  });

  return obj;
}

//plumbing
console = {
  _createConsole: function() {
    var pre = document.createElement('pre');
    pre.setAttribute('id', 'console');
    document.body.insertBefore(pre, document.body.firstChild);
    return pre;
  },
  info: function(message) {
    var pre = document.getElementById("console") || console._createConsole();
    pre.textContent += ['>', message, '\n'].join(' ');
  }
};

//test case
console.info(JSON.stringify(lowerObjKeys({
  "StackOverflow": "blah",
  "Test": {
    "LULZ": "MEH"
  }
}), true));

Beware, it doesn't track circular references, so you can end up with an infinite loop resulting in stack overflow.