I have a PHP function that returns a multiple-level JSON object in the format

var data = {
  1 : { 
    1: { Object },
    2: { Object },
     ...,
     ...
  }, 
  2: {
    1: { Object },
    2: { Object },
    ...,
    ...
  }
}

I need to get the length of data to initialize a for loop maximum value. By this, I mean the count of the first level entries.

data[1].length returns 22, and data[2].length returns 23 via the console.log printout. This is expected, but data.length returns undefined.

Is there a better method than

var count = 0;

for (var i=1; i< Number.MAX_VALUE; i++){
  if (typeof data[i] != 'undefined')
    count = i;
}

I have a PHP function that returns a multiple-level JSON object in the format

var data = {
  1 : { 
    1: { Object },
    2: { Object },
     ...,
     ...
  }, 
  2: {
    1: { Object },
    2: { Object },
    ...,
    ...
  }
}

I need to get the length of data to initialize a for loop maximum value. By this, I mean the count of the first level entries.

data[1].length returns 22, and data[2].length returns 23 via the console.log printout. This is expected, but data.length returns undefined.

Is there a better method than

var count = 0;

for (var i=1; i< Number.MAX_VALUE; i++){
  if (typeof data[i] != 'undefined')
    count = i;
}

• javascript
• arrays
• json

• is there any way you can store your data in an array of objects instead of an object? – dm03514 Commented Aug 30, 2012 at 16:33
• I really don't have control over that part at this time, unfortunately. – Jason Commented Aug 30, 2012 at 16:38

4 Answers 4

How About

Object.keys(data).length

If you can control the JSON format, nested arrays seem a better alternative.

If not, you can run something like

var length = 0;
for (var i in data) {
    if (isFinite(i) && i > length)
        length = i;
}

You can count the number of entries in a loop, like this:

var length = 0;
for (var key in data) {
  if (data.hasOwnProperty(key)) {
    length++;
  }
}

However, if you have control over the returned data, it would probably be easier to return an array instead of an object because the array will already have the length property you want.

Why not just do this instead of assigning numeric properties? Arrays will have the length property you wish:

var data = [
  [ 
    { Object },
    { Object },
     ...,
     ...
  ], 
  [
    { Object },
    { Object },
    ...,
    ...
  ]
]