Count JavaScript object value in array for duplicates

Question

Hello I am new to the community and this is my first question.

/// I have an array of objects. Will be a few hundred at some point.

var locations = [{
    "name": "Costco",
    "city": "San Francisco",
    "state": "CA",
    "zip": "75201",
}, {
    "name": "Safeway",
    "city": "Appleton",
    "state": "WI",
    "zip": "90210",
}, {
    "name": "Foodmart",
    "city": "Orlando",
    "state": "FL",
    "zip": "90210",
}, {
    "name": "Trader Joes",
    "city": "Concord",
    "state": "CA",
    "zip": "90210",
}];

/// I need to count each "state:" and hold the value as a variable like below.

var CA
/// Value would be 2

var FL
/// Value would be 1

var WI
/// Value would be 1

/// forgive me, I am a bit rusty with array's

Do you need to store the state count in individual variables or would an obj work states={'CA':2,'FL':1,etc} — depperm
– depperm, Commented Dec 8, 2015 at 19:09
I need 48 individual variables. That will be rendered on load. One variable for each state. — Jean-Luc-Picard
– Jean-Luc-Picard, Commented Dec 8, 2015 at 19:12
could I ask why you need 48 individual variables instead on one object variable? — depperm
– depperm, Commented Dec 8, 2015 at 19:15
The variable will be sent to a canvas gaming engine that will use these values for each state. The javascript that is used to read values in this engine are limited. — Jean-Luc-Picard
– Jean-Luc-Picard, Commented Dec 8, 2015 at 19:17

Sterling Archer · Accepted Answer · 2015-12-08 19:29:03Z

6

Using a simple loop, you can do this. (This uses ES6 arrow function syntax, and let. Easily replaced by var and anonymous function syntax for older browser compatibility)

let states = {};

locations.forEach(obj => {
    if (states[obj.state]) states[obj.state]++;
    else states[obj.state] = 1;
});

This loops over the array, checks to see if an entry exists in your counter object, and if it does, increment the count, otherwise add the entry and set it to 1.

Note that I used an object to store the counts, instead of individual variables. It's less messy and easier indexing this way.

edited Dec 8, 2015 at 19:29

answered Dec 8, 2015 at 19:13

Sterling Archer

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10 Comments

Jean-Luc-Picard Over a year ago

Question: So how would I isolate each state and write its count value? To give a better idea of what I am doing. In my Canvas creative I am rendering icons for each state. If the states value is greater or equal to 1 I generate a marker that displays that states total. In my example above, California would have a (2) icon since its count is (2) and my desired variable CA = 2.

Sterling Archer Over a year ago

Here's an output of my script: Object {CA: 2, WI: 1, FL: 1}. Assuming you assign it to states, it's as easy as var countForCA = states["CA"];

Jean-Luc-Picard Over a year ago

Thanks, I will see if I can get this to work in a jsfiddle. But it will take me awhile.

Jean-Luc-Picard Over a year ago

started a JSfiddle but I am doing it wrong :( - jsfiddle.net/jean_luc_picard/30bdf7h2/33

Sterling Archer Over a year ago

@Jean-Luc-Picard you're trying to access the count for CA before it's even created/populated (you're also using strings incorrectly) "states" is a string and has no "CA" property. remove the quotes around states and put it after the loop

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Jean-Luc-Picard · Accepted Answer · 2015-12-08 20:30:24Z

Thanks to "Sterling Archer"... This is solved. Fiddle: http://jsfiddle.net/30bdf7h2/48/

// LIST

var locations = [{
  "name": "Costco",
  "city": "San Francisco",
  "state": "CA",
  "zip": "75201",
}, {
  "name": "Safeway",
  "city": "Appleton",
  "state": "WI",
  "zip": "90210",
}, {
  "name": "Foodmart",
  "city": "Orlando",
  "state": "FL",
  "zip": "90210",
}, {
  "name": "Trader Joes",
  "city": "Concord",
  "state": "CA",
  "zip": "90210",
}];

var states = {};
locations.forEach(obj => {
  if (states[obj.state]) states[obj.state]++;
  else states[obj.state] = 1;
});

var countForCA = states["CA"];

magic();
function magic() {
  document.getElementById("state_total").innerHTML = "CA Count: "+countForCA;
  document.getElementById("array_total").innerHTML = "Array Total: " + locations.length;
}

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