Get length of array inside object

Question

i have the following object in javascript:

objectX which is an

Object {names : Array[14]}

im trying to get the length of this, but it returns undefined when i use objectX.length?

Im trying it in chrome debugger, and googling, anyone out there quickly let me know plz.

• BenM: Do you want the number of properties in Object, or the length of Object.names?
• user1555190: length of names @BenM
• BenM: See the answer posted already, then.
• user1636522: objectX | objectx?

Answer 1

object.names.length

OR

object['names'].length

• user1555190: If i use objectx.names it returns undefined
• adamb: Then your object is defined differently than the code you presented. (you'll need to replace "object" with whatever variable name you're using... perhaps objectx.names.length)
• user1555190: Okay if i use Object.keys(objectx).length, this returns me 1. But i want the length of names. Which it says is an array in chrome

Answer 2

From the output it seems that the property name is 'name '. See the differences in the console output:

> console.log({names: []});
Object {names: Array[0]}
> console.log({'names ': []});
Object {names : Array[0]} // <- this looks like what you have
// ^ note the space

So you'd have to do:

obj['names '].length

I suggest to fix the property name though, so that you can use obj.name.length instead.

• user1555190: thankyou, i just didn't think of that! grrrr spent last 20 minutes not even looking at that!
• Felix Kling: Next time you know ;)

Answer 3

Fix your object notation:

var obj = {name:Array(14)};
alert(obj.name.length);
var obj = {name : [1, 2, 3, 4]};
alert(obj.name.length);

Fiddle

• Felix Kling: Object {names : Array[14]} is the output in Chrome's console. It's not actually JS code.
• Dave Rager: @FelixKling Ok, I misunderstood. Though I didn't think a space was valid in a property name.
• Felix Kling: You can use any string as property name. But if the property is not a valid identifier, then you cannot use dot notation (a.b) to access it, you have to use bracket notation (a['b']).
• Dave Rager: @FelixKling interesting. I learned something new today, thanks!