Get Object Size

As in, the number of keys.

function objectSize(the_object) {
  /* function to validate the existence of each key in the object to get the number of valid keys. */
  var object_size = 0;
  for (key in the_object){
    if (the_object.hasOwnProperty(key)) {
  return object_size;


// Arbitrary object
var something = {
  dog: "cat",
  cat: "dog"

// Logs: 2


  1. code200
    Permalink to comment#

    Be sure to add var in front of key in your loop:

    for (var key in the_object){

    so the variable key goes out of scope with the function.

    Most recent browsers support this shorter version:
  2. Dwight Vietzke
    Permalink to comment#

    Just ran across this post while debugging code for IE. IE versions before 9 seem to have a problem with Object.keys and .hasOwnProperty used directly on an object. So a more sophisticated replacement is necessary, which can be found here:

    Hope this helps.

  3. Sam Purcell
    Permalink to comment#

    I like this Chris, but it seems more correct to add it to the Object prototype. IE

    Object.prototype.size = function() {
    var size = 0
    // your code, but using "this"

    return size;
    Called with something.size()

    From what I understand, adding a new function to the object prototype should not be a problem.

    • Michael Caputo
      Permalink to comment#

      Hey Sam, could you write out your suggestion? I’m a bit confused by this.

      Thanks for the help.

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