javascriptarraysreducearrayofarrays

Regroup array of objects based on nested array


I have an Array of Object. Each Object contains another inner Array. I would like to take each inner array as outer object and put the remaining old outer elements as sub properties of newly created outer object.

Input

data = [
    {
      name: "Sam",
      ssn: 123,
      age: 25,
      hobbies: [{ name: "cricket" }, { name: "football" }]
    },
    {
      name: "John",
      ssn: 234,
      age: 25,
      hobbies: [{ name: "cricket" }, { name: "football" }]
    },
    {
      name: "Mathew",
      ssn: 345,
      age: 25,
      hobbies: [{ name: "cricket" }, { name: "football" }, {name: "carroms"}]
    }
  ];

Expected Output

[
      {
        name: "cricket",
        person_details: [
          { name: "Sam", ssn: 123, age: 25 },
          { name: "John", ssn: 234, age: 25 },
          { name: "Mathew", ssn: 345, age: 25 }
        ]
      },
      {
        name: "football",
        person_details: [
          { name: "Sam", ssn: 123, age: 25 },
          { name: "John", ssn: 234, age: 25 },
          { name: "Mathew", ssn: 345, age: 25 }
        ]
      },
      {
        name: "carroms",
        person_details: [          
          { name: "Mathew", ssn: 345, age: 25 }
        ]
      }
    ]

What i have tried using Reduce as follows

this.data = this.data.reduce(
  (a, x) => [...x.hobbies.map(h => ({ ...x, hobbies: [h] }))],
  []
);

Solution

  • You could reduce the array and look for same name items for the result set.

    var data = [{ name: "Sam", ssn: 123, age: 25, hobbies: [{ name: "cricket" }, { name: "football" }] }, { name: "John", ssn: 234, age: 25, hobbies: [{ name: "cricket" }, { name: "football" }] }, { name: "Mathew", ssn: 345, age: 25, hobbies: [{ name: "cricket" }, { name: "football" }, { name: "carroms" }] }],
        result = data.reduce((r, { hobbies, ...o }) => {
            hobbies.forEach(({ name }) => {
                var group = r.find(q => q.name === name);
                if (!group) r.push(group = { name, person_details: [] });
                group.person_details.push(o);
            })
            return r;
        }, []);
    
    console.log(result);
    .as-console-wrapper { max-height: 100% !important; top: 0; }