Calculate the number of elements shared between two arrays using JavaScript

I am working with two arrays of objects and I need to determine how many different types of cars we have.

The first array contains the IDs of all the cars, while the second array contains information about the types of cars.

Here is the data:

var arr = {
    "categories": [{
        "id": "100",
        "name": "category name",
        "car_id": "1"
    }, {
        "id": "192",
        "name": "category name here",
        "car_id": "25"      
    }, {
        "id": "192",
        "name": "category name here",
        "car_id": "27"      
    }]
};


var arr2 = {
    "cars": [{
        "id": "1",
        "name": "car name",
        "car_id": "1",
        "type": "ford"
    }, {
        "id": "4",
        "name": "name 2",
        "car_id": "25",
        "type": "ford"      
    }, {
        "id": "4",
        "name": "name 2",
        "car_id": "27",
        "type": "fiat"      
    }]
};

Since there are only 5 types of cars, I have created 5 variables:

var:

ford,
fiat,
mazda,
mini,
mg

My goal is to end up with something like this:

ford: 2;
fiat: 1;
mazda: 0;
mini: 0;
mg: 0;

Can someone guide me on how to achieve this?

javascriptarraysjson

Answer №1

For a fixed number of types, consider using this method

Create a map initially

var map = {
  ford: 0,
  fiat: 0,
  mazda: 0,
  mini: 0,
  mg: 0
};

Then go through the arrays and tally up the types

arr2.cars.forEach(function(item) {
  map[item.type]++;
});

Your map now contains the counts by type.

var arr2 = {
  "cars": [{
    "id": "1",
    "name": "car name",
    "car_id": "1",
    "type": "ford"
  }, {
    "id": "4",
    "name": "name 2",
    "car_id": "25",
    "type": "ford"
  }, {
    "id": "4",
    "name": "name 2",
    "car_id": "27",
    "type": "fiat"
  }]
};
var map = {
  ford: 0,
  fiat: 0,
  mazda: 0,
  mini: 0,
  mg: 0
};

arr2.cars.forEach(function(item) {
  map[item.type]++;
});

console.log(map);

Answer №2

const categoryArr = {
    "categories": [{
        "id": "100",
        "name": "category name",
        "car_id": "1"
    }, {
        "id": "192",
        "name": "category name here",
        "car_id": "25"      
    }, {
        "id": "192",
        "name": "category name here",
        "car_id": "27"      
    }]
};

const carArr = {
    "cars": [{
        "id": "1",
        "name": "car name",
        "car_id": "1",
        "type": "ford"
    }, {
        "id": "4",
        "name": "name 2",
        "car_id": "25",
        "type": "ford"      
    }, {
        "id": "4",
        "name": "name 2",
        "car_id": "27",
        "type": "fiat"      
    }]
};

let carCount, typeCount;

categoryArr.categories.forEach(function(item){
    if(item.hasOwnProperty("car_id")){
         carCount = categoryArr.categories.length;
    }
});

carArr.cars.forEach(function(item){
    if(item.hasOwnProperty("type")){
         typeCount = carArr.cars.length;
    }
});

console.log(carCount);
console.log(typeCount);

https://jsfiddle.net/Law7rzc2/

Answer №3

Everything you require is

calculateTotal(arr2.cars, 'type')

The completion of calculateTotal is a task for the reader.

Answer №4

Array.prototype.reduce is the ideal function to use for performing array computations like this. Utilizing a Map can assist in keeping track of the distinct car makes as you loop through the array of cars.

var obj2 = {
    "cars": [{
        "id": "1",
        "name": "car name",
        "car_id": "1",
        "type": "ford"
    }, {
        "id": "4",
        "name": "name 2",
        "car_id": "25",
        "type": "ford"      
    }, {
        "id": "4",
        "name": "name 2",
        "car_id": "27",
        "type": "fiat"      
    }]
};

const typeStat = cars => {
  let map = cars.reduce((m, {type}) =>
    m.set(type, (m.get(type) || 0) + 1), new Map());
  return Array.from(map, ([make, count]) => ({make, count}));
};

let stats = typeStat(obj2.cars)

console.log(stats);

Output

[
  {
    "make": "ford",
    "count": 2
  },
  {
    "make": "fiat",
    "count": 1
  }
]

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