Count-keys NPM

count-keys

A JS function for counting the number of keys there are in objects and arrays, including nested objects and arrays.

npm install count-keys --save

The first parameter in countKeys is the object you wish to count the number of keys in. The second parameter takes various options that allow you to control the output.

countKeys(object, [options])

Default functionality

By default, every key in the object will increase the increment of the return value by 1. If a value in the object is another object, it will also count all the keys in that child object. Since arrays are essentially objects with numbered keys (['a', 'b','c'] being similar to {0:'a', 1:'b', 2:'c'}) this will also count array items by default.

var countKeys = require('count-keys');

var object = {
  one: {
    two : 'string',
    three : {
      four: ['five', 'six']
    }
  },
  seven: 'string',
  eight: {
    nine : 'string',
  }
}

var keyCount = countKeys(object);

// keyCount = 9

Excluding arrays

Arrays and objects aren't exactly the same thing though so it's understandable that you might not want to include array items in the index count. To turn off array counting, use the arrays setting.

var countKeys = require('count-keys');

var object = {
  one: {
    two : 'string',
    three : {
      four: ['string', 'string']
    }
  },
  five: 'string',
  six: {
    seven : 'string',
  }
}

var keyCount = countKeys(object, { arrays: false })

// keyCount = 7

Excluding sub-objects

Maybe you don't want to know how deep the rabit hole goes. Maybe you just want to count the blades of grass at the entrance. For a simple top level only counting of the number of keys there are in an object, set recursive to false.

var countKeys = require('count-keys');

var object = {
  one: {
    keyA : 'string',
    keyB : {
      keyC: ['string', 'string']
    }
  },
  two: 'string',
  three: {
    keyD : 'string',
  }
}

var keyCount = countKeys(object, { recursive: false })

// keyCount = 3

Excluding keys below a certain depth

Similar to recursive:false. maxDepth will allow you to define a specific depth that you do not want to surpass when counting. maxDepth:1 is essentially the same as recursive:false.

var countKeys = require('count-keys');

var object = {
  one: {
    two : 'string',
    three : {
      keyA: ['string', 'string']
    }
  },
  four: 'string',
  five: {
    six : 'string',
  }
}

var keyCount = countKeys(object, { maxDepth: 2 })

// keyCount = 6

Custom filtering

If you aren't happy with the results you are getting back from the function, you might need to do custom filtering.

var countKeys = require('count-keys');

var object = {
  one: {
    a : 'string',
    two : {
      three: ['four', 'five']
    }
  },
  b: 'string',
  six: {
    c : 'string',
  }
}

var keyCount = countKeys(object, { filter: function(item){
    // available values in "item":
    // item.key, item.value, item.count, item.parent, item.depth

    if (item.value === 'string') return false;

    //The filter will default to "true" if it returns "undefined"
}})

// keyCount = 6

These are the values you have available to you in the "item" variable: