Guide on extracting unique identifiers from an array of objects and sorting them by the earliest date in JavaScript

Question

Guide on extracting unique identifiers from an array of objects and sorting them by the earliest date in JavaScript

I've got an array of objects and I'm looking to retrieve the items with unique IDs while also selecting the earliest date.

For example: [{id:1, date: Jan 12}, {id:2, date: Feb 8}, {id:3, date: Feb 8}]

var array = [{id: 1, date: Jan 12 2021 08:00:00 AM}, {id: 2, date: Feb 8 2021 08:00:00 AM}, {id: 2, date: Mar 2 2021 08:00:00 AM}, {id: 3, date: Feb 8 2021 08:00:00 AM}]

Edit: I forgot to mention that the date format is a string formatted as moment("MM-DD-YYYY");

This is what I have so far:

var withId = array.filter(function (g) { return g.Id != null });

withId = array.filter(function (e) { return moment(e.UtcStart) < moment() && e.DteEndDate != null ? moment(e.DteEndDate) > moment() : true });

withId.sort(function (a, b) { return moment(a.UtcStart) - moment(b.UtcStart) });

var key = 'Id';

var unique = [...new Map(withId.map(x => [x[key], x])).values()];

javascript

Answer 1

Answer №1

To achieve the desired outcome, you can utilize the Array.reduce() method. By iterating through each item in the array, we create a map based on the unique identifier id. If the date of the current item is earlier than the existing entry in the map at acc[id], we replace it:

var data = [{id: 1, date: 'Jan 12 2021 08:00:00 AM'}, {id: 2, date: 'Feb 8 2021 08:00:00 AM'}, {id: 2, date: 'Mar 2 2021 08:00:00 AM'}, {id: 3, date: 'Feb 8 2021 08:00:00 AM'}];

const result = Object.values(data.reduce((acc, { id, date }) => { 
    if (!acc[id] || Date.parse(acc[id].date) > Date.parse(date)) acc[id] = { id, date };
    return acc;
}, {}));

console.log('Final Result:', result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

To achieve the desired outcome, you can utilize the Array.reduce() method. By iterating through each item in the array, we create a map based on the unique identifier id. If the date of the current item is earlier than the existing entry in the map at acc[id], we replace it:

var data = [{id: 1, date: 'Jan 12 2021 08:00:00 AM'}, {id: 2, date: 'Feb 8 2021 08:00:00 AM'}, {id: 2, date: 'Mar 2 2021 08:00:00 AM'}, {id: 3, date: 'Feb 8 2021 08:00:00 AM'}];

const result = Object.values(data.reduce((acc, { id, date }) => { 
    if (!acc[id] || Date.parse(acc[id].date) > Date.parse(date)) acc[id] = { id, date };
    return acc;
}, {}));

console.log('Final Result:', result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 3

Answer №2

To order your array according to dates is essential.

let array = [{id: 1, date: 'Jan 12 2021 08:00:00 AM'}, {id: 2, date: 'Feb 8 2021 08:00:00 AM'}, {id: 2, date: 'Mar 2 2021 08:00:00 AM'}, {id: 3, date: 'Feb 8 2021 08:00:00 AM'}]
let sortedArray = array.sort((a, b) => new Date(b.date) - new Date(a.date))// reverse sorting for Map to retain last value of same key
let twoDeimentionalArray = sortedArray.map(item=>[item.id,item.date])
let map = new Map(twoDeimentionalArray)//Create a set

and focus on it.

Moreover

var array = [
{id: 1, date: 'Jan 12 2021 08:00:00 AM'}, 
{id: 2, date: 'Feb 8 2021 08:00:00 AM'}, 
{id: 2, date: 'Mar 2 2020 08:00:00 AM'}, 
{id: 3, date: 'Feb 8 2021 08:00:00 AM'},
{id: 2, date: 'July 8 2022 08:00:00 AM'},
{id: 4, date: 'Feb 8 2021 08:00:00 AM'}
]
let sortedArray = array.sort((a, b) => (new Date(a.date) - new Date(b.date))).sort((a, b) => (a.id- b.id))

const reducedArray = sortedArray.reduce(function(set,item){
    return (set.length !== 0 && set[set.length-1].id == item.id) ?  set : set.concat(item)
},new Array)
console.log(sortedArray)
console.log(reducedArray)

Answer 4

To order your array according to dates is essential.

let array = [{id: 1, date: 'Jan 12 2021 08:00:00 AM'}, {id: 2, date: 'Feb 8 2021 08:00:00 AM'}, {id: 2, date: 'Mar 2 2021 08:00:00 AM'}, {id: 3, date: 'Feb 8 2021 08:00:00 AM'}]
let sortedArray = array.sort((a, b) => new Date(b.date) - new Date(a.date))// reverse sorting for Map to retain last value of same key
let twoDeimentionalArray = sortedArray.map(item=>[item.id,item.date])
let map = new Map(twoDeimentionalArray)//Create a set

and focus on it.

Moreover

var array = [
{id: 1, date: 'Jan 12 2021 08:00:00 AM'}, 
{id: 2, date: 'Feb 8 2021 08:00:00 AM'}, 
{id: 2, date: 'Mar 2 2020 08:00:00 AM'}, 
{id: 3, date: 'Feb 8 2021 08:00:00 AM'},
{id: 2, date: 'July 8 2022 08:00:00 AM'},
{id: 4, date: 'Feb 8 2021 08:00:00 AM'}
]
let sortedArray = array.sort((a, b) => (new Date(a.date) - new Date(b.date))).sort((a, b) => (a.id- b.id))

const reducedArray = sortedArray.reduce(function(set,item){
    return (set.length !== 0 && set[set.length-1].id == item.id) ?  set : set.concat(item)
},new Array)
console.log(sortedArray)
console.log(reducedArray)

Answer 5

Answer №3

Is eliminating the later date with the same ID a viable solution?

var array = [{id: 1, date: "Jan 12 2021 08:00:00 AM"}, {id: 2, date: "Feb 8 2021 08:00:00 AM"}, {id: 2, date: "Mar 2 2021 08:00:00 AM"}, {id: 3, date: "Feb 8 2021 08:00:00 AM"}]
var uniqMap = {};
array.forEach(v => {
    if (!uniqMap[v.id] || (Date.parse(v.date) < Date.parse(uniqMap[v.id]))) {
        uniqMap[v.id] = v;
    }
})
console.log(uniqMap);
// convert map to array
var uniqIds = Object.keys(uniqMap).map((key) => uniqMap[key]);
console.log(uniqMap);

// output displayed:
0: {id: 1, date: 'Jan 12 2021 08:00:00 AM'}
1: {id: 2, date: 'Feb 8 2021 08:00:00 AM'}
2: {id: 3, date: 'Feb 8 2021 08:00:00 AM'}

Answer 6

Is eliminating the later date with the same ID a viable solution?

var array = [{id: 1, date: "Jan 12 2021 08:00:00 AM"}, {id: 2, date: "Feb 8 2021 08:00:00 AM"}, {id: 2, date: "Mar 2 2021 08:00:00 AM"}, {id: 3, date: "Feb 8 2021 08:00:00 AM"}]
var uniqMap = {};
array.forEach(v => {
    if (!uniqMap[v.id] || (Date.parse(v.date) < Date.parse(uniqMap[v.id]))) {
        uniqMap[v.id] = v;
    }
})
console.log(uniqMap);
// convert map to array
var uniqIds = Object.keys(uniqMap).map((key) => uniqMap[key]);
console.log(uniqMap);

// output displayed:
0: {id: 1, date: 'Jan 12 2021 08:00:00 AM'}
1: {id: 2, date: 'Feb 8 2021 08:00:00 AM'}
2: {id: 3, date: 'Feb 8 2021 08:00:00 AM'}

Guide on extracting unique identifiers from an array of objects and sorting them by the earliest date in JavaScript

Answer №1

Answer №2

Answer №3

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