Question

155

JavaScript Group By Array

rated 0 times [ 158] [ 3] / answers: 1 / hits: 59962 / 12 Years ago, sat, october 13, 2012, 12:00:00

Possible Duplicate:

array_count_values for javascript instead

Let's say I have simple JavaScript array like the following:

var array = ['Car', 'Car', 'Truck', 'Boat', 'Truck'];

I want to group and count of each so I would expect a key/value map of:

{

  Car   : 2,

  Truck : 2,

  Boat  : 1

}

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micayla

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answered 12 Years ago noa · Accepted Answer

var arr = [ 'Car', 'Car', 'Truck', 'Boat', 'Truck' ];

var hist = {};

arr.map( function (a) { if (a in hist) hist[a] ++; else hist[a] = 1; } );

console.log(hist);

results in

{ Car: 2, Truck: 2, Boat: 1 }

This works, too:

hist = arr.reduce( function (prev, item) { 

  if ( item in prev ) prev[item] ++; 

  else prev[item] = 1; 

  return prev; 

}, {} );