How to get unique category data from array of objects

Question

I have an object like this:

data.bills = [
    { date: '2018-01-20', amount: '220', category: 'Electricity' ,categoryId: '48' },
    { date: '2018-01-20', amount: '20', category: 'Gas' ,categoryId: '16' },
    { date: '2018-02-20', amount: '120', category: 'Electricity' ,categoryId: '48' }
]

Now i want to create a new array from this like this(Req Output):

data.allUniqueCategories = [
    {category: 'Electricity' ,categoryId: '48'},
    { category: 'Gas' ,categoryId: '16'}
]

I tried something like this but its becoming too complex can anyone tell the simple solution thanks..

function _toConsumableArray(arr) { 
    if (Array.isArray(arr)) { 
        for (var i = 0, arr2 = Array(arr.length); i < arr.length; i++) {
        arr2[i] = arr[i]; } 
        return arr2; 
        } else {
    return Array.from(arr); } 
}

c.data.categories = [].concat(_toConsumableArray(new Set(data.bills.map(function (bill) {
    return bill.state;
}))));

console.log(c.data.categories);
//['Electricity','Gas']

but i want in this format

//[{category: 'Electricity' ,categoryId: '48'},{ category: 'Gas' ,categoryId: '16'}]

Possible duplicate of [Get all unique values in a JavaScript array (remove duplicates)](https://stackoverflow.com/questions/1960473/get-all-unique-values-in-a-javascript-array-remove-duplicates) — Jeff, Oct 21 '18 at 10:57

score 2 · Answer 1 · answered Oct 21 '18 at 10:59

data.bills = [
    { date: '2018-01-20', amount: '220', category: 'Electricity' ,categoryId: '48' },
    { date: '2018-01-20', amount: '20', category: 'Gas' ,categoryId: '16' },
    { date: '2018-02-20', amount: '120', category: 'Electricity' ,categoryId: '48' }
]
data.allUniqueCategories = [...new Set(data.bills.map(o => o.category));

Here map is getting categories and adding to the new Set, Set can contain only unique values, so if there will be duplicate categories, it will not be added in Set, after finishing map it will spread Set values into new array by this operator ...

score 1 · Answer 2 · answered Oct 21 '18 at 11:04

You can reduce the bills into an object with the category as the key, and than convert to array using Object.values():

const bills = [{"date":"2018-01-20","amount":"220","category":"Electricity","categoryId":"48"},{"date":"2018-01-20","amount":"20","category":"Gas","categoryId":"16"},{"date":"2018-02-20","amount":"120","category":"Electricity","categoryId":"48"}]

const allUniqueCategories = Object.values(bills.reduce((r, { category, categoryId }) => {
  r[category] = { category, categoryId };

  return r;
}, {}));

console.log(allUniqueCategories);

score 1 · Answer 3 · answered Oct 21 '18 at 11:04

You could use reduce method with Map as accumulator param to create unique array by category and categoryId props.

const bills = [
  { date: '2018-01-20', amount: '220', category: 'Electricity' ,categoryId: '48' },
  { date: '2018-01-20', amount: '20', category: 'Gas' ,categoryId: '16' },
  { date: '2018-02-20', amount: '120', category: 'Electricity' ,categoryId: '48' }
]

const uniq = bills.reduce((r, {category, categoryId}) => {
  let key = `${category}|${categoryId}`;
  r.set(key, (r.get(key) || {category, categoryId}));
  return r;
}, new Map())

console.log([...uniq.values()])

score 1 · Accepted Answer · answered Oct 21 '18 at 11:04

Use Array#reduce() to create an object with the categories as keys and get the values of that object as result

const bills = [
    { date: '2018-01-20', amount: '220', category: 'Electricity' ,categoryId: '48' },
    { date: '2018-01-20', amount: '20', category: 'Gas' ,categoryId: '16' },
    { date: '2018-02-20', amount: '120', category: 'Electricity' ,categoryId: '48' }
]

const res = Object.values(bills.reduce((a,{category,categoryId})=>{
   a[category]={category, categoryId}
   return a;
},{}))

console.log(res)

How to get unique category data from array of objects

4 Answers4