Iterating through list of keys for associative array in JSON

Question

I have an associative array in JSON

var dictionary = {"cats":[1,2,37,38,40,32,33,35,39,36], "dogs", [4,5,6,3,2]};

Can I get the keys from this? I tried in Visual studio putting a breakpoint but can't see any property that represents keys. Is it not possible?

I'm fine creating a separate array if necessary, but was just hoping it wasnt :

var keys = ["cats", "dogs"];

Answer 1

Try this:

var keys = [];
for (var key in dictionary) {
  if (dictionary.hasOwnProperty(key)) {
    keys.push(key);
  }
}

Answer 2

for (var key in dictionary) {
  // do something with key
}

It's the for..in statement.

Answer 3

Just a quick note, be wary of using for..in if you use a library (jQuery, prototype, etc.), as most of them add methods to created Objects (including dictionaries).

This will mean that when you loop over them, method names will appear as keys. If you are using a library, look at the documentation and look for an enumerable section, where you will find the right methods for iteration of your objects.