lodash - group and populate arrays

Question

Using lodash, how could I group the names of people that have the same birthdates as seen below?

I wrote this out using nested for loops but was thinking there would be a more elegant way of doing this in lodash. I haven't used it much and trying to figure out which function to use.

[
    { "birthdate": "1993", "name": "Ben" },
    { "birthdate": "1994", "name": "John" },
    { "birthdate": "1995", "name": "Larry" },
    { "birthdate": "1995", "name": "Nicole" },
    { "birthdate": "1996", "name": "Jane" },
    { "birthdate": "1996", "name": "Janet" },
    { "birthdate": "1996", "name": "Dora" },
]

to

[
    { "birthdate": "1993", "names": [ "Ben" ] }, 
    { "birthdate": "1994", "names": [ "John"] },
    { "birthdate": "1995", "names": [ "Larry", "Nicole" ] }, 
    { "birthdate": "1996", "names": [ "Jane", "Janet", "Dora" ] }        
]

score 20 · Accepted Answer · answered Feb 07 '17 at 06:41

You can use groupBy() to group each item in the collection by birthdate. After grouping the items, you can use map() to iterate each groups and form them into a new format that includes a birthdate and names. To acquire an array of names from the grouped items, you can use the map() function again to return all the name values.

var result = _(source)
    .groupBy('birthdate')
    .map(function(items, bdate) {
      return {
        birthdate: bdate,
        names: _.map(items, 'name')
      };
    }).value();

var source = [
    { "birthdate": "1993", "name": "Ben" },
    { "birthdate": "1994", "name": "John" },
    { "birthdate": "1995", "name": "Larry" },
    { "birthdate": "1995", "name": "Nicole" },
    { "birthdate": "1996", "name": "Jane" },
    { "birthdate": "1996", "name": "Janet" },
    { "birthdate": "1996", "name": "Dora" },
];
  
var result = _(source)
    .groupBy('birthdate')
    .map(function(items, bdate) {
      return {
        birthdate: bdate,
        names: _.map(items, 'name')
      };
    }).value();

document.body.innerHTML = '<pre>' + JSON.stringify(result, 0, 4) + '</pre>';

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>

@ballar Thanks It worked for me but Is there any way to group elements by date only where in the array of objects we have a dateTime property... refer : (https://stackoverflow.com/questions/48562519/how-to-group-elements-using-lodash-group-by-angular-2-4) — Aakriti.G, Feb 02 '18 at 06:35

score 3 · Answer 2 · answered Feb 07 '17 at 06:28

3

You can chain groupBy and map to achieve this.

_.chain(yourArray)
.groupBy('birthdate')
.toPairs()
.map(s=>{
return _.zipObject(['birthdate','names'],s)
})
.map(s=>{
s.names=_.map(s.names,x=>x.name);
return s;
})
.value()

answered Feb 07 '17 at 06:28

Waqas Noor

911
6
12

Divyesh Kanzariya · Answer 3 · 2019-05-02T13:23:14.773

You can use reduce() and find()

   let arr = [{
 "birthdate": "1993",
 "name": "Ben"
},
{
 "birthdate": "1994",
 "name": "John"
},
{
 "birthdate": "1995",
 "name": "Larry"
},
{
 "birthdate": "1995",
 "name": "Nicole"
},
{
 "birthdate": "1996",
 "name": "Jane"
},
{
 "birthdate": "1996",
 "name": "Janet"
},
{
 "birthdate": "1996",
 "name": "Dora"
},
];

const res = arr.reduce((ac, a) => {
let temp = ac.find(x => x.birthdate === a.birthdate);
if (!temp) ac.push({ ...a,
 name: [a.name]
})
else temp.name.push(a.name)
return ac;
}, [])
console.log(res);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js"></script>

score 1 · Answer 4 · answered Mar 26 '20 at 01:42

An simple and customizable pure javascript function to return an array of objects grouped by the attribute needed in the object

export const groupArrayBy = (arr, groupBy) => {

    let newArr = []
    arr.map((item) => {
        if(item[groupBy]) {
            let finded = newArr.filter((newItem) => newItem[groupBy] === item[groupBy])
            if(finded.length > 0) {
                finded[0].products.push(item)
            } else {
                newArr.push({category: item[groupBy], products: [item]})
            }
        }
    })

    return newArr
}

score 0 · Answer 5 · answered Nov 03 '20 at 12:00

Lodash shortand

var data=[
    { "birthdate": "1993", "name": "Ben" },
    { "birthdate": "1994", "name": "John" },
    { "birthdate": "1995", "name": "Larry" },
    { "birthdate": "1995", "name": "Nicole" },
    { "birthdate": "1996", "name": "Jane" },
    { "birthdate": "1996", "name": "Janet" },
    { "birthdate": "1996", "name": "Dora" },
];


var list= _(data)
    .groupBy('birthdate')
    .map((items, birthdate)=> ({birthdate: birthdate,names: _.map(items, 'name')
      })).value();
      
      console.log(list)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js"></script>

lodash - group and populate arrays

5 Answers5

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