How to count JavaScript array objects?

Question

When I have a JavaScript array like this:

var member = {
    "mother": {
        "name" : "Mary",
        "age" : "48"
    },
    "father": {
        "name" : "Bill",
        "age" : "50"
    },
    "brother": {
        "name" : "Alex",
        "age" : "28"
    }
}

How to count objects in this array?!
I mean how to get a counting result 3, because there're only 3 objects inside: mother, father, brother?!

If it's not an array, so how to convert it into JSON array?

Answer 1

That's not an array, is an object literal, you should iterate over the own properties of the object and count them, e.g.:

function objectLength(obj) {
  var result = 0;
  for(var prop in obj) {
    if (obj.hasOwnProperty(prop)) {
    // or Object.prototype.hasOwnProperty.call(obj, prop)
      result++;
    }
  }
  return result;
}

objectLength(member); // for your example, 3

The hasOwnProperty method should be used to avoid iterating over inherited properties, e.g.

var obj = {};
typeof obj.toString; // "function"
obj.hasOwnProperty('toString'); // false, since it's inherited

Answer 2

Here's how I'd do it

function getObjectLength( obj )
{
  var length = 0;
  for ( var p in obj )
  {
    if ( obj.hasOwnProperty( p ) )
    {
      length++;
    }
  }
  return length;
}

Answer 3

That is not an array, it is an object literal.

You can iterate the objects properties and count how many it owns:

var count = 0;
for (var k in obj) {
  // if the object has this property and it isn't a property
  // further up the prototype chain
  if (obj.hasOwnProperty(k)) count++;
}

Answer 4

Thats not an array. Its an object literal. An array would look like this

var members = [

    {"mother": {"name" : "Mary", "age" : "48" }},
    {"father": {"name" : "Bill", "age" : "50" }},
    {"brother": {"name" : "Alex", "age" : "28" }}

];