Count object property inside array using lodash or vanilla javascript

Question

I have this object with nested arrays/objects:

{
"USA": [
    {
        "location": "New York",
        "municipality": "Manhattan",
    },
    {
        "location": "Texas",
        "municipality": "Austin",
    }
  ],
"CANADA": [
    {
        "location": "Ontario",
        "municipality": "no municipality",
    }
  ]
}

I want to use lodash or plain javascript to count how many location are inside the USA and CANADA. How is that possible?

desired result:

USA: 2
CANADA: 1

Cerbrus · Accepted Answer · 2017-06-30 11:20:10Z

3

Just use the array lengths:

var USA = myObj.USA.length;
var Canada = myObj.CANADA.length;

Or, for larger data sets:

var result = {};
Object.keys(myObj)
    .forEach(function(key,index) {
        result[key] = myObj[key].length;
    });

edited Jun 30, 2017 at 11:20

answered Jun 30, 2017 at 11:17

Cerbrus

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2 Comments

Stathis Ntonas Over a year ago

i want to iterate, the array has ~400 objects

Cerbrus Over a year ago

@StathisNtonas: Added an example for that.

Gruff Bunny · Accepted Answer · 2017-06-30 11:25:04Z

3

With lodash you could use mapValues:

let result = _.mapValues(data, 'length');

answered Jun 30, 2017 at 11:25

Gruff Bunny

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Comments

RomanPerekhrest · Accepted Answer · 2017-06-30 11:51:53Z

2

The solution using Array.prototype.reduce() function:

var obj = {
        "USA": [ { "location": "New York", "municipality": "Manhattan" }, { "location": "Texas", "municipality": "Austin" } ], "CANADA": [ { "location": "Ontario", "municipality": "no municipality" }] 
    },

    result = Object.keys(obj).reduce(function(r,k){
        r[k] = obj[k].length;
    	return r;
    }, {});

console.log(result)

answered Jun 30, 2017 at 11:51

RomanPerekhrest

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