Counting the number of properties in a JavaScript object

Question

So I have this JavaScript literal that is displaying a tree structure using arborjs.

var data = {
    "nodes": {
        You: {
            'color': 'green',
            'shape': 'dot',
            'label': 'You'
        },
        Ben: {
            'color': 'black',
            'shape': 'dot',
            'label': 'Ben'
        },
        David: {
            'color': 'black',
            'shape': 'dot',
            'label': 'David'
        }
    },
    "edges": {
        You: {
            Ben: {},
            David: {}
        },
        Ben: {
            David: {}
        }
    }
};

I want to count the number of properties in the nodes object (3 in this case) and number of properties in the edges object (2 in this case) to display some statistics for the user tree. I output the data variable using ruby on rails by recursively going over my database and creating a hash. But before, should I count the nodes client side or server side? Should I go over the database again and count statistics or just count the properties?

take a look at this: http://stackoverflow.com/questions/126100/how-to-efficiently-count-the-number-of-keys-properties-of-an-object-in-javascrip — Igor Dymov, Nov 22 '11 at 15:20

score 3 · Accepted Answer · answered Nov 22 '11 at 15:20

3

to count the nodes you can do

var count=0;
for(node in data.nodes)
    count++;

answered Nov 22 '11 at 15:20

Manuel van Rijn

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score 1 · Answer 2 · answered Nov 22 '11 at 15:23

You could do something like this:

var data = {
                   "nodes":{
                    "You":{'color':'green','shape':'dot','label':'You'},
                     Ben:{'color':'black','shape':'dot','label':'Ben'},
                     David:{'color':'black','shape':'dot','label':'David'}
                   }, 
                   "edges":{
                     You:{ Ben:{}, David:{} },
                     Ben:{ David:{}}
                   }
                 };
Object.prototype.NosayrCount = function () {
    var count = 0;
    for(var i in this)
        if (this.hasOwnProperty(i))
            count++;
    return count;
}

data.NosayrCount(); // 2
data.Nodes.NosayrCount(); // 3
data.edges.NosayrCount(); // 2

Counting the number of properties in a JavaScript object

2 Answers2