Count Key/Values in JSON [duplicate]

Question

Possible Duplicate:
Length of Javascript Associative Array

I have a JSON that looks like this:

Object:
   www.website1.com : "dogs"
   www.website2.com : "cats"
   >__proto__ : Object

This prints when I do this:

console.log(obj);

I am trying to get the count of the items inside this JSON, obj.length returns "undefined" and obj[0].length returns

Uncaught TypeError: Cannot read property 'length' of undefined

I would expect a length to return "2" in this case. How can I find the count?

Thanks!

yep i can delete, maybe the other question should be retitled, its a bit deceiving since js doesn't even have associative arrays — Doug Molineux
– Doug Molineux, Commented Jun 9, 2011 at 0:56

davin · Accepted Answer · 2011-06-08 18:38:56Z

32

You have to count them yourself:

function count(obj) {
   var count=0;
   for(var prop in obj) {
      if (obj.hasOwnProperty(prop)) {
         ++count;
      }
   }
   return count;
}

Although now that I saw the first comment on the question, there is a much nicer answer on that page. One-liner, probably just as fast if not faster:

function count(obj) { return Object.keys(obj).length; }

Be aware though, support for Object.keys() doesn't seem cross-browser just yet.

edited Jun 8, 2011 at 18:38

answered Jun 8, 2011 at 18:33

davin

45.6k9 gold badges81 silver badges78 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Eric Over a year ago

Did you mean to pass Object.keys the count function?

davin Over a year ago

@Eric, nope, I sure didn't. Cheers.

GabLeRoux Over a year ago

Thanks, maybe it's not cross-browser yet, but works well in node.js server side ;)

Eric · Accepted Answer · 2011-06-08 18:33:11Z

7

.length only works on arrays, not objects.

var count = 0;
for(var key in json)
    if(json.hasOwnProperty(key))
        count++;

answered Jun 8, 2011 at 18:33

Eric

98.1k54 gold badges257 silver badges389 bronze badges

Collectives™ on Stack Overflow

Count Key/Values in JSON [duplicate]

2 Answers 2

3 Comments

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Linked

Related