Create a new array from an existing array of objects

Question

Hi I have an array of objects such as this:

const data = [ {day: "Monday", to: "12.00", from: "15.00"}, {day: "Monday", to: "18.00", from: "22.00"}, {day: "Tuesday", to: "12.00", from: "22.00"}]

I need to make a new array from this existing one and have it like below. I know I need to use .map method to create a new array, but my knowledge beyond this is lacking. Really appreciate it if someone could guide me in the right direction please.

Example of new array I want:

const newArr = [{"Monday":[{"12.00", "15.00"}, {"18.00", "22.00"}], {"Tuesday": ["9.00", "5.00"]}]

Your `newArr` isn't valid JavaScript. You probably want a new array that's an array of objects. — JoshG, Sep 09 '20 at 18:31
@AndroidNoobie, i knew my syntax was not right thanks for pointing that out. — , Sep 09 '20 at 18:34
@EmileBergeron You are brilliant, that's what i need thank you so much! — , Sep 09 '20 at 18:40
@apena thanks for pointing that out, i was missing a bracket. — , Sep 09 '20 at 18:42

Sascha · Accepted Answer · 2020-09-09T19:00:14.550

Using Array#reduce to iterate over your array and accumulte the desired data. Look for every day if there exists in the accumulted dresult-object an property with this day as keyname. If not then create it with an object with again the day as property and an empty array . In all cases add to this array your times.
At last use Object#values to get the values out of it.

const data = [ {day: "Monday", to: "12.00", from: "15.00"}, {day: "Monday", to: "18.00", from: "22.00"}, {day: "Tuesday", to: "12.00", from: "22.00"}];

let res = Object.values(data.reduce((acc, cur) => {
    if (!acc[cur.day]) {
        acc[cur.day] = {[cur.day]: []};
    }
    acc[cur.day][cur.day].push([cur.to, cur.from]);
    return acc;
}, {}));


console.log(res);

Create a new array from an existing array of objects

1 Answers1