CODEWITHSUNDEEP
javascriptarrayssorting
Alex Ironside
Alex Ironside

Reputation: 5039

Sort array by child's child

The situation is: I have an array of objects, in which every object has an array of objects. The array looks like this:

[
    {
        "dislikes": [
            {
                "createDate": {
                    "date": 11,
                    "day": 0,
                    "hours": 18,
                    "minutes": 15,
                    "month": 10,
                    "seconds": 11,
                    "time": 1541956511001,
                    "timezoneOffset": -60,
                    "year": 118
                },
            },
            {
                "createDate": {
                    "date": 11,
                    "day": 0,
                    "hours": 18,
                    "minutes": 15,
                    "month": 10,
                    "seconds": 11,
                    "time": 1541956511008,
                    "timezoneOffset": -60,
                    "year": 118
                },
            }
        ],
    },
    {
        "dislikes": [
            {
                "createDate": {
                    "date": 11,
                    "day": 0,
                    "hours": 18,
                    "minutes": 15,
                    "month": 10,
                    "seconds": 11,
                    "time": 1541956511011,
                    "timezoneOffset": -60,
                    "year": 118
                },
            },
            {
                "createDate": {
                    "date": 11,
                    "day": 0,
                    "hours": 18,
                    "minutes": 15,
                    "month": 10,
                    "seconds": 11,
                    "time": 1541956511028,
                    "timezoneOffset": -60,
                    "year": 118
                },
            }
        ],
    }
]

So I want to sort the users, and the dislikes by the time in their dislikes. So the user with the earliest dislike would be first, as well as the earliest dislike would be first in each users' dislikes array. I believe I have to do multiple sorts, but how can I do that exactly?

Upvotes: 0

Views: 64

Answers (4)

Kruthika C S
Kruthika C S

Reputation: 739

//Supply the array you've metioned as the argument users to the below method, sortDislikesForAllUsers 
let sortDislikesForAllUsers = function(users) {
    return users.map(user => {
        return {
            dislikes: user.dislikes.sort((dislikeA, dislikeB) => ((dislikeA.createDate.time < dislikeB.createDate.time) ? -1 : (dislikeA.createDate.time > dislikeB.createDate.time) ? 1 : 0))
        }
    })
}
//Supply the array returned in the above method as input to the below method, sortUsers
let sortUsers = function(arrayOfSortedDislikesPerUser) {
    return arrayOfSortedDislikesPerUser.sort((userA, userB) => ((userA.dislikes[0].createDate.time < userB.dislikes[0].createDate.time) ? -1 : (userA.dislikes[0].createDate.time > userB.dislikes[0].createDate.time) ? 1 : 0))
}

let arrayOfSortedDislikesPerUser = sortDislikesForAllUsers(users);
let finalSortedArray = sortUsers(arrayOfSortedDislikesPerUser);
console.log(finalSortedArray);

In the below snippet,
sortDislikesForAllUsers This method sorts the dislikes for individual users

sortUsers This method sorts the users based on the first dislike time of the sorted dislikes array obtained from the above method

Simple :)

Run the below snippet. You can directly copy paste it in your code!

    let users = [{
        "dislikes": [
            {
                "createDate": {
                    "date": 11,
                    "day": 0,
                    "hours": 18,
                    "minutes": 15,
                    "month": 10,
                    "seconds": 11,
                    "time": 1541956511001,
                    "timezoneOffset": -60,
                    "year": 118
                },
            },
            {
                "createDate": {
                    "date": 11,
                    "day": 0,
                    "hours": 18,
                    "minutes": 15,
                    "month": 10,
                    "seconds": 11,
                    "time": 1541956511008,
                    "timezoneOffset": -60,
                    "year": 118
                },
            }
        ],
    },
    {
        "dislikes": [
            {
                "createDate": {
                    "date": 11,
                    "day": 0,
                    "hours": 18,
                    "minutes": 15,
                    "month": 10,
                    "seconds": 11,
                    "time": 1541956511011,
                    "timezoneOffset": -60,
                    "year": 118
                },
            },
            {
                "createDate": {
                    "date": 11,
                    "day": 0,
                    "hours": 18,
                    "minutes": 15,
                    "month": 10,
                    "seconds": 11,
                    "time": 1541956511028,
                    "timezoneOffset": -60,
                    "year": 118
                },
            }
        ],
    }]

    let sortDislikesForAllUsers = function(users) {
	    return users.map(user => {
		    return {
			    dislikes: user.dislikes.sort((dislikeA, dislikeB) => ((dislikeA.createDate.time < dislikeB.createDate.time) ? -1 : (dislikeA.createDate.time > dislikeB.createDate.time) ? 1 : 0))
		    }
	    })
    }

    let sortUsers = function(arrayOfSortedDislikesPerUser) {
	    return arrayOfSortedDislikesPerUser.sort((userA, userB) => ((userA.dislikes[0].createDate.time < userB.dislikes[0].createDate.time) ? -1 : (userA.dislikes[0].createDate.time > userB.dislikes[0].createDate.time) ? 1 : 0))
    }

    let arrayOfSortedDislikesPerUser = sortDislikesForAllUsers(users);
    let finalSortedArray = sortUsers(arrayOfSortedDislikesPerUser);
    console.log(finalSortedArray);

EDIT: WRT to the comment by @HMR:
1. It mutates the original array. Yes. If you want to avoid mutation, you must create a copy of the sent array. let noRefCopy = new Array() noRefCopy = noRefCopy.concat(originalArr)
Now, perform sorting on the copy and return the same.

2. If you wanna have checks for undefined etc, sure you can.

The above answer attempts to address the logic. Sure we can address the above 2 concerns if the question is really specific to them.

Cheers,
Kruthika

Upvotes: 2

HMR
HMR

Reputation: 39270

You can map the items and add a property to it containing the earliest dislike and then sort on that:

const data = [{"dislikes":[{"createDate":{"date":11,"day":0,"hours":18,"minutes":15,"month":10,"seconds":11,"time":1541956511001,"timezoneOffset":-60,"year":118}},{"createDate":{"date":11,"day":0,"hours":18,"minutes":15,"month":10,"seconds":11,"time":1541956511008,"timezoneOffset":-60,"year":118}}]},{"dislikes":[{"createDate":{"date":11,"day":0,"hours":18,"minutes":15,"month":10,"seconds":11,"time":1541956511011,"timezoneOffset":-60,"year":118}},{"createDate":{"date":11,"day":0,"hours":18,"minutes":15,"month":10,"seconds":11,"time":1541956511028,"timezoneOffset":-60,"year":118}}]}];

console.log(
  data
    //map and add newestDislike property
    .map((d) => ({
      ...d,
      //reduce and only takes the lowest time value
      newestDislike: (d.dislikes || []).reduce(
        (result, item) =>
          item.createDate.time < result
            ? item.createDate.time
            : result,
        Infinity, //defaults to infinity (if no dislikes)
      ),
    }))
    .sort((a, b) => a.newestDislike - b.newestDislike),
);

If the dislikes in the user are already sorted by oldest date first then you can skip the map and reduce part. If a user can have empty dislikes or undefined then make sure you use a getter function with a default so your code won't crash:

//gets a nested prop from object or returns defaultValue
const get = (o = {}, path, defaultValue) => {
  const recur = (o, path, defaultValue) => {
    if (o === undefined) return defaultValue;
    if (path.length === 0) return o;
    if (!(path[0] in o)) return defaultValue;
    return recur(o[path[0]], path.slice(1), defaultValue);
  };
  return recur(o, path, defaultValue);
};
console.log(
  data.sort(
    (a, b) =>
      get(
        a,
        ['dislikes', 0, 'createDate', 'time'],
        Infinity,
      ) -
      get(
        b,
        ['dislikes', 0, 'createDate', 'time'],
        Infinity,
      ),
  ),
);

Upvotes: 2

dRoyson
dRoyson

Reputation: 1507

Check the code below. This will let you sort based on time:

function sortByTime(obj1, obj2){
  return obj1.time - obj2.time;
}

array.sort((obj1, obj2)=>{
  obj1.dislikes.sort(sortByTime);
  obj2.dislikes.sort(sortByTime);
  return obj1.dislikes[0].time - obj2.dislikes[0].time;
});

I did not get what you meant by earliest time. The above code sorts time in ascending order.

NOTE: The above code does not handle edge cases where a property night be missing

Upvotes: 1

Andrey
Andrey

Reputation: 2068

Something like as follows (with lodash.js)

_.each(users, (u) => { u.dislikes = _.sortBy(u.dislikes, 'createdDate.time'); });
users = _.sortBy(users, 'dislikes[0].createdDate.time');

Upvotes: 1

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