Convert array into shorter array

Question

I have array object -

[
 { 
  department:"Reviewer",
  name:"John"
 },
 { 
  department:"Reviewer",
  name:"Carol"
 },
 { 
  department:"Reviewer",
  name:"June"
 },
 { 
  department:"Assistant Reviewer",
  name:"Mac"
 },
 { 
  department:"Assistant Reviewer",
  name:"Issac"
 }
]

I want to convert this object into array object as below -

[
     { 
      department:"Reviewer",
      name:"John;Carol;June;"
     },
     { 
      department:"Assistant Reviewer",
      name:"Mac;Issac;"
     },
]

I tried using filter -

[... new Set(obj.department)].map((item)=>{return {item.name+";"} });

But this operation is dealing with only one element per item. Its not accumulating names.

Possible duplicate of How to group by and sum an array of objects? and Group by similar attribute and join them by comma javascript - Mysql group concat like — adiga
– adiga, Commented Feb 3, 2023 at 6:23
@Unmitigated it's the exact same operators. Use + operator on strings instead of numbers. This is probably a better target: Group by similar attribute and join them by comma javascript - Mysql group concat like — adiga
– adiga, Commented Feb 3, 2023 at 6:26

Andrew Parks · Accepted Answer · 2023-02-03 07:16:59Z

2

Get a set of distinct departments, then map from them to the list of names

const data = [{"department":"Reviewer","name":"John"},{"department":"Reviewer","name":"Carol"},{"department":"Reviewer","name":"June"},{"department":"Assistant Reviewer","name":"Mac"},{"department":"Assistant Reviewer","name":"Issac"}]

console.log([...new Set(data.map(i=>i.department))].map(i=>({
  department: i, 
  name: data.filter(j=>j.department===i).map(j=>j.name).join(';')+';'})))

or, using reduce:

const data = [{"department":"Reviewer","name":"John"},{"department":"Reviewer","name":"Carol"},{"department":"Reviewer","name":"June"},{"department":"Assistant Reviewer","name":"Mac"},{"department":"Assistant Reviewer","name":"Issac"}]

console.log(Object.values(data.reduce((a,{department, name})=>
  (((a[department]??={department,name:''}).name+=`${name};`),a),{})))

edited Feb 3, 2023 at 7:16

answered Feb 3, 2023 at 7:03

Andrew Parks

8,1672 gold badges22 silver badges35 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Amila Senadheera · Accepted Answer · 2023-02-03 06:41:38Z

1

This would also work:

const input = [ { department: "Reviewer", name: "John", }, { department: "Reviewer", name: "Carol", }, { department: "Reviewer", name: "June", }, { department: "Assistant Reviewer", name: "Mac", }, { department: "Assistant Reviewer", name: "Issac", }, ];

const output = input.reduce((prev, { department, name }) => {
  const match = prev.find((item) => item.department === department);
  if (match) {
    match.name = `${match.name};${name}`;
  } else {
    prev.push({ department, name });
  }
  return prev;
}, []);

console.log(output);

Using Array.prototype.reduce() and Array.prototype.find()

answered Feb 3, 2023 at 6:41

Amila Senadheera

13.4k16 gold badges31 silver badges48 bronze badges

Comments

Peter Thoeny · Accepted Answer · 2023-02-03 07:10:30Z

Here is a solution using:

.reduce() to build an object that maps from department (aka key) to names (aka value)
.map() to transform that object into an array of objects with desired format

Note that this solution is faster than an array index search (aka other answers here) for large a large input array, at the cost of using a bit more memory.

const array = [
  { department: "Reviewer", name: "John" },
  { department: "Reviewer", name: "Carol" },
  { department: "Reviewer", name: "June" },
  { department: "Assistant Reviewer", name: "Mac" },
  { department: "Assistant Reviewer", name: "Issac" }
];

const result = Object.entries(array.reduce((acc, obj) => {
  if(acc[obj.department]) {
    acc[obj.department] += obj.name + ';';
  } else {
    acc[obj.department] = obj.name + ';';
  }
  return acc;
}, {})).map(arr => ({ department: arr[0], name: arr[1] }));

console.log(result);

Jordy · Accepted Answer · 2023-02-03 07:27:51Z

1

This codes should work:

let data = [
  { department: "Reviewer", name: "John" },
  { department: "Reviewer", name: "Carol" },
  { department: "Reviewer", name: "June" },
  { department: "Assistant Reviewer", name: "Mac" },
  { department: "Assistant Reviewer", name: "Issac" }
];

let newData = [];
data.forEach((obj)=>{
  if(newData.filter(m => m.department == obj.department).length) {
    newData.find(n => n.department == obj.department).name += obj.name + ';'; 
  } else {
    newData.push({
      department: obj.department,
      name: obj.name + ';'
    })
  } 
});
console.log(newData);

edited Feb 3, 2023 at 7:27

answered Feb 3, 2023 at 7:19

Jordy

2,0473 gold badges12 silver badges40 bronze badges

Collectives™ on Stack Overflow

Convert array into shorter array

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related