Javascript - How to count the unique ID (value) from Array of Objects within Array reduce() method

Question

Hi I have been practicing challenges on reduce method to really understand it but this subject has confused me.

const orders = [
    {  livingId: 996, cash: 30500.35, tax: 0.06, isDisputed: true},
    {  livingId: 910, cash: 100, tax: 0.08, isDisputed: true },
    {  livingId: 912, cash: 4200.11, tax: 0.06 },
    {  livingId: 996, cash: 99.12, tax: 0.06, isDisputed: false },
    {  livingId: 910, cash: 0.00, tax: 0.08, isShipped: true },
    {  livingId: 996, cash: 10, tax: 0.06, isDisputed: true },
];

const result = orders.reduce(
    (arr, current) => {
        const numOrders = arr.numOrders + 1;
        const uniqueId = [...new Set([current.livingId])] //returns [996]
        console.log("arr.uniqueId= "+ arr.uniqueId)
        console.log("current.livingId= "+ current.livingId)  
        console.log("current.livingId  + arr.uniqueId= "+ uniqueId)
 return {
            numOrders,
            uniqueId,
        };
    },
    {
        numOrders: 0, 
        uniqueId: 0,
    },
);

console.log(result)

How do I return the total count of UNIQUE id values from livingId? Together with my current method of getting total orders.

Expected result: NumOrders: 6 livingId: 3

I have tried console logging multiple methods like filter, includes and found the cleanest is the new Set method but it only returns the last iterable array from livingId returning [996]. Returning .length will definitely be 1 instead not 3. I also tried this but it returns back all the values instead.

const uniqueId = [...new Set([arr.uniqueId, current.livingId])] // 0,996,910,912,996,910,996

Andy · Accepted Answer · 2022-09-25 09:18:34Z

2

If you want to do this with reduce:

const orders=[{livingId:996,cash:30500.35,tax:.06,isDisputed:!0},{livingId:910,cash:100,tax:.08,isDisputed:!0},{livingId:912,cash:4200.11,tax:.06},{livingId:996,cash:99.12,tax:.06,isDisputed:!1},{livingId:910,cash:0,tax:.08,isShipped:!0},{livingId:996,cash:10,tax:.06,isDisputed:!0}];

const ids = orders.reduce((set, c) => {
  set.add(c.livingId);
  return set;
}, new Set());

console.log(ids.size);

Alternatively: map over the array to get an array of ids, add that array to a set, and get its size.

const orders = [
  {  livingId: 996, cash: 30500.35, tax: 0.06, isDisputed: true},
  {  livingId: 910, cash: 100, tax: 0.08, isDisputed: true },
  {  livingId: 912, cash: 4200.11, tax: 0.06 },
  {  livingId: 996, cash: 99.12, tax: 0.06, isDisputed: false },
  {  livingId: 910, cash: 0.00, tax: 0.08, isShipped: true },
  {  livingId: 996, cash: 10, tax: 0.06, isDisputed: true }
];

const idsLen = new Set(orders.map(order => order.livingId)).size;

console.log(idsLen);

answered Sep 25, 2022 at 9:18

Andy

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1 Comment

LukeLuc Over a year ago

thanks! The alternative map solution worked placing it inside of the reduce method helps return the unique count to its respective key in my original code.

Shivangam Soni · Accepted Answer · 2022-09-25 09:22:14Z

1

const orders = [
    {  livingId: 996, cash: 30500.35, tax: 0.06, isDisputed: true},
    {  livingId: 910, cash: 100, tax: 0.08, isDisputed: true },
    {  livingId: 912, cash: 4200.11, tax: 0.06 },
    {  livingId: 996, cash: 99.12, tax: 0.06, isDisputed: false },
    {  livingId: 910, cash: 0.00, tax: 0.08, isShipped: true },
    {  livingId: 996, cash: 10, tax: 0.06, isDisputed: true },
];

const uniqueIds = orders.reduce((acc, val) => {
  if(!acc.includes(val.livingId)) {
    acc.push(val.livingId);
  }
  return acc
}, []);

const count = uniqueIds.length;

console.log(uniqueIds, count);

answered Sep 25, 2022 at 9:22

Shivangam Soni

7067 silver badges16 bronze badges

Comments

flyingfox · Accepted Answer · 2022-09-25 10:28:13Z

Another solution for you

const orders = [
        {  livingId: 996, cash: 30500.35, tax: 0.06, isDisputed: true},
        {  livingId: 910, cash: 100, tax: 0.08, isDisputed: true },
        {  livingId: 912, cash: 4200.11, tax: 0.06 },
        {  livingId: 996, cash: 99.12, tax: 0.06, isDisputed: false },
        {  livingId: 910, cash: 0.00, tax: 0.08, isShipped: true },
        {  livingId: 996, cash: 10, tax: 0.06, isDisputed: true },
    ];

    const result = orders.reduce((acc,val) => {
       let uniqueId = val.livingId
       let obj = acc.find(a => a.uniqueId == val.livingId)
       if(!!obj){
          obj.numOrders++
       }else{
          acc.push({numOrders: 1, uniqueId: uniqueId})
       }
       return acc
    },[]);

 console.log(result)

Test Result

[
  {
    "numOrders": 3,
    "uniqueId": 996
  },
  {
    "numOrders": 2,
    "uniqueId": 910
  },
  {
    "numOrders": 1,
    "uniqueId": 912
  }
]

peejay · Accepted Answer · 2022-09-25 11:24:14Z

And one more solution based on reduce() and Map.

With this solution, you can get the number of unique ids and also a breakdown of the number of orders with the same unique id.

const orders = [
    {  livingId: 996, cash: 30500.35, tax: 0.06, isDisputed: true},
    {  livingId: 910, cash: 100, tax: 0.08, isDisputed: true },
    {  livingId: 912, cash: 4200.11, tax: 0.06 },
    {  livingId: 996, cash: 99.12, tax: 0.06, isDisputed: false },
    {  livingId: 910, cash: 0.00, tax: 0.08, isShipped: true },
    {  livingId: 996, cash: 10, tax: 0.06, isDisputed: true },
];

const map = orders.reduce((map, item) => {
    if(map.has(item.livingId)) {
        map.set(item.livingId, map.get(item.livingId) + 1);
    } else {
        map.set(item.livingId, 1);
    }
    return map;
}, new Map());

console.log("Unique Ids:", map.size);

const array = Array.from(map);

console.log(array);

The solution using Map can be enhanced to keep a running total of cash and tax (ignoring the fact that we should not be using floating points for storing money values).

const orders = [
    {  livingId: 996, cash: 30500.35, tax: 0.06, isDisputed: true},
    {  livingId: 910, cash: 100, tax: 0.08, isDisputed: true },
    {  livingId: 912, cash: 4200.11, tax: 0.06 },
    {  livingId: 996, cash: 99.12, tax: 0.06, isDisputed: false },
    {  livingId: 910, cash: 0.00, tax: 0.08, isShipped: true },
    {  livingId: 996, cash: 10, tax: 0.06, isDisputed: true },
];

const map = orders.reduce((map, item) => {
    if(map.has(item.livingId)) {
        const {cash, tax} = map.get(item.livingId);
        map.set(item.livingId, {cash: cash + item.cash, tax: tax + item.tax });
    } else {
        map.set(item.livingId, {cash: item.cash, tax: item.tax });
    }
    return map;
}, new Map());

console.log("Unique Ids:", map.size);

const array = Array.from(map);

console.log(array);

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