How to find the length of a JSON object

Question

 var legend=[{"min":0,
            "max":first_color,
            "color":"#1a9850"
  },
  {
      "min":first_color,
      "max":sec_color,
      "color":"#fee08b"
  },
  {
      "min":sec_color,
      "max":thrd_color,
      "color":"#ff3300"
  },
  {
      "min":thrd_color,
      "max":frth_color,
      "color":"#d73027"
      "Abc":"gsfg"
  }

  ];

I'd like to find out each object's property count. E.g. the first 3 objects have 3 properties and 4th one has 4 props, etc.

1. Iterate 2. Get current element in array 3. `Object.keys(arrayEl).length` — Tushar, Nov 16 '16 at 06:07
Where are you stuck? Are you having a problem looping over the elements/objects in the array? Are you having a problem getting the list of each object's keys? — , Nov 16 '16 at 06:11
Objects don't have "lengths". They have some number of properties. — , Nov 16 '16 at 06:15
Currently you have an array of Objects so 1. iterating over the array: `for(var i = 0; i < legend.length; i++) { // Code that does something with each object here}` 2. find how many keys in that particular object - `Object.keys(legend[i]),length` OR iterate over each key and do something with it `for(var key in legend[i]){ console.log(legend[i][key]) }` 3. make it more readable - within 1. you could do `var currentLegend = legend[i];` then use that instead in 2. especially if you need to do more than just count the keys — Brian, Nov 16 '16 at 06:21

score 11 · Accepted Answer · answered Nov 16 '16 at 06:09

11

Iterate over the array and get object property names count.

var legend = [{
  "min": 0,
  "max": 'first_color',
  "color": "#1a9850"
}, {
  "min": 'first_color',
  "max": 'sec_color',
  "color": "#fee08b"
}, {
  "min": 'sec_color',
  "max": 'thrd_color',
  "color": "#ff3300"
}, {
  "min": 'thrd_color',
  "max": 'frth_color',
  "color": "#d73027",
  "Abc": "gsfg"
}];

var res = legend.map(function(v) {
  console.log(Object.keys(v).length);
  return Object.keys(v).length;
});

console.log(res);

answered Nov 16 '16 at 06:09

Pranav C Balan

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I really must remember to use map more +1 for a nice clean solution! – Brian Nov 16 '16 at 06:26
one more silly question what if i want to know which field are persent in json array in first there are min max and color and in fourth one min max color and Abc etc – Gaurav Singh Nov 16 '16 at 06:29
coz for iterating object we must know key – Gaurav Singh Nov 16 '16 at 06:31
`Object.keys` returns an array of keys so you can iterate over that using either `map` again or a regular `for` loop. – Brian Nov 16 '16 at 06:35
@GauravSingh : check `console.log(Object.keys(v))` – Pranav C Balan Nov 16 '16 at 06:37
1

thx you so much.............. – Gaurav Singh Nov 16 '16 at 06:50

score 7 · Answer 2 · edited May 23 '17 at 10:33

7

'JSON' object is the wrong terminology.
Referring to 'Length of a JavaScript object', the best solution would be:

Object.keys(obj).length

But a better solution would be to prototype Object

Object.size = function(obj) {
   return Object.keys(obj).length;
}

edited May 23 '17 at 10:33

Community

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1

answered Nov 16 '16 at 06:09

Amit

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Why is that a better solution? – Nov 16 '16 at 06:14
@torazaburo Because it would be cleaner for more than 1 usage. Object.size(obj) is simpler and more human readable. – Amit Nov 16 '16 at 06:16

score 4 · Answer 3 · answered Nov 16 '16 at 06:10

4

you can use Object.keys

 console.log(Object.keys(legend[0]).length)// 3

 console.log(Object.keys(legend[3]).length);//4

answered Nov 16 '16 at 06:10

Deep

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How to find the length of a JSON object

3 Answers3