How to Find the max value of an attribute in an array of objects

user_13333147 0
Viewed 137

I have an array of objects like below,

[
    {
        id: 1,
        holiday_for: 1,
        holiday_on: "2021-10-26"
    },
    {
        id: 2,
        holiday_for: 3,
        holiday_on: "2021-10-26"
    },
    {
        id: 3,
        holiday_for: 1,
        holiday_on: "2021-11-26"
    },
    {
        id: 4,
        holiday_for: 3,
        holiday_on: "2021-11-26"
    },
    {
        id: 5,
        holiday_for: 4,
        holiday_on: "2021-11-26"
    }
]

where the objects have the same dates but different holiday_for. holiday_for has 3 types 1, 3, 4. I am trying to find an object with the same dates which has max holiday_for.

If the array has 2 objects with the same dates and types 1 and 3 then 3 will get high priority. If it has 3 objects with the same dates with types 1, 3, 4 then 4 will get priority.

I have tried using reduce but it returns only the object with the highest type -

const filtered = holidays.reduce((max, cur) =>
    max.holiday_for > cur.holiday_for ? max : cur
)

Output type

[
        
        {
            id: 2,
            holiday_for: 3,
            holiday_on: "2021-10-26"
        },
        {
            id: 5,
            holiday_for: 4,
            holiday_on: "2021-11-26"
        }
    ]
typescript javascript
3 Answers
  1. Sort If the holidays have the same holiday_on, So Sort holiday_for By Descending Order.
holidays_sorted = holidays.sort((a,b)=>{
    if(a.holiday_on === b.holiday_on){
        return b.holiday_for - a.holiday_for
    }
})
  1. Filter uniques holiday_on
let unique = {};
holidays_sorted = holidays.filter(holiday=> {
    if (unique[holiday.holiday_on]) {
        return false;
    }
    unique[holiday.holiday_on] = true;
    return true;
});

//keep first unique holiday_on for each date Which is the higher
{id: 2, holiday_for: 3, holiday_on: '2021-10-26'}//<--this
{id: 1, holiday_for: 1, holiday_on: '2021-10-26'}
{id: 5, holiday_for: 4, holiday_on: '2021-11-26'}//<--that
{id: 4, holiday_for: 3, holiday_on: '2021-11-26'}
{id: 3, holiday_for: 1, holiday_on: '2021-11-26'}

Result:

{id: 2, holiday_for: 3, holiday_on: '2021-10-26'}
{id: 5, holiday_for: 4, holiday_on: '2021-11-26'}
user_145297790

As I am using Angular needed to add some types. Based on @Mehdi Taher answer I have added some typing and ended up like this -

const sortedHolidays = holidays.sort(
    (a: IHoliday, b: IHoliday) => {
        return a.holiday_on === b.holiday_on
            ? b.holiday_for - a.holiday_for
            : 0;
    }
);

let unique: { [key: string]: IHoliday | boolean } = {};
    const filtered = duplicateHolidays.filter(
    (holiday: IHoliday) => {
        if (unique[holiday.holiday_on]) {
            return false;
        }
        unique[holiday.holiday_on] = true;
        return true;
    }
);
user_133331470

If I understand correctly, something like the below.

let ordered = array
   .filter(a => a.holiday_on == "2021-11-26")
   .sort((a, b) => b.holiday_for - a.holiday_for);

let priority = ordered[0].holiday_for;

ordered.filter(a => a.holiday_for == priority);
user_75282620
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