29

Possible Duplicate:
How to efficiently count the number of keys/properties of an object in JavaScript? 

var values = [{
    'SPO2': 222.00000,
    'VitalGroupID': 1152,
    'Temperature': 36.6666666666667,
    'DateTimeTaken': '/Date(1301494335000-0400)/',
    'UserID': 1,
    'Height': 182.88,
    'UserName': null,
    'BloodPressureDiastolic': 80,
    'Weight': 100909.090909091,
    'TemperatureMethod': 'Oral',
    'Resprate': null,
    'HeartRate': 111,
    'BloodPressurePosition': 'Standing',
    'VitalSite': 'Popliteal',
    'VitalID': 1135,
    'Laterality': 'Right',
    'HeartRateRegularity': 'Regular',
    'HeadCircumference': '',
    'BloodPressureSystolic': 120,
    'CuffSize': 'XL'
}];

for (i=0; i < values.length; i++) {
        alert(values.length) // gives me 2.

How can find how many keys my object has?

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3
  • 1
    Two things: 1) Why are you looping through values.length yet also alerting values.length? 2) I swear values.length is not going to give you 2. Commented Jul 17, 2011 at 11:49
  • stackoverflow.com/questions/5223/… Commented Jul 17, 2011 at 11:50
  • 1
    Further to @BoltClock's comment, alert(values.length); gives: 1. And, incidentally, from my own training, the saturated partial arterial pressure of oxygen (SPO2), should be a percentage value of up to 100 (percent, obviously). Where's the 222.00000 coming from? I'm not intending to be confrontational, but I am curious... =) Commented Jul 17, 2011 at 11:51

4 Answers 4

Reset to default
74 
var value = {
    'SPO2': 222.00000,
    'VitalGroupID': 1152,
    'Temperature': 36.6666666666667,
    'DateTimeTaken': '/Date(1301494335000-0400)/',
    'UserID': 1,
    'Height': 182.88,
    'UserName': null,
    'BloodPressureDiastolic': 80,
    'Weight': 100909.090909091,
    'TemperatureMethod': 'Oral',
    'Resprate': null,
    'HeartRate': 111,
    'BloodPressurePosition': 'Standing',
    'VitalSite': 'Popliteal',
    'VitalID': 1135,
    'Laterality': 'Right',
    'HeartRateRegularity': 'Regular',
    'HeadCircumference': '',
    'BloodPressureSystolic': 120,
    'CuffSize': 'XL'
};

alert(Object.keys(value).length);
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1 Comment

How can i find the total number of keys if the Object is inside an array
7

try

Object.keys(values).length

see: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/keys

for compatiblity

if(!Object.keys) Object.keys = function(o){
 if (o !== Object(o))
      throw new TypeError('Object.keys called on non-object');
 var ret=[],p;
 for(p in o) if(Object.prototype.hasOwnProperty.call(o,p)) ret.push(p);
 return ret;
}

or use:

function numKeys(o){
var i=0;
for(p in o) if(Object.prototype.hasOwnProperty.call(o,p)){ i++};
return i;
}
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1 Comment

which you should attribute to its source...
5 
function numKeys(o) {
   var res = 0;
   for (var k in o) {
       if (o.hasOwnProperty(k)) res++;
   }
   return res;
}

or, in newer browsers:

function numKeys(o) {
   return Object.keys(o).length;
}

In your example, values is an array with one element, so you'd call numKeys(values[0]) to find out.

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1 Comment

#2 should be Object.keys(o).length
-2

You can iterate and just count:

var i = 0;
for(var key in values[0]) if(values[0].hasOwnProperty(key)) i++;
// now i is amount
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3 Comments

This will include properties defined by the object prototype
@phihag: You're correct but you should not extend Object.prototype anyway.
@pimvdb indeed you shouldn't, but you should program defensively in case one of the libraries you're using has.

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