Merge Objects in Array with Similar Key in JavaScript

Let’s say, we have the following array of objects −

const arr = [
   {id: 1, h1: 'Daily tests'},
   {id: 2, h1: 'Details'},
   {id: 1, h2: 'Daily classes'},
   {id: 3, h2: 'Results'},
   {id: 2, h3: 'Admissions'},
   {id: 1, h4: 'Students'},
   {id: 2, h5: 'Alumni'},
   {id: 3, h3: 'Appreciations'},
   {id: 1, h5: 'Tiny Tots'},
   {id: 1, h6: 'Extras'},
];

We have to write a function that converts this array into an array where all the headings (h1, h2, h3 …) that have the same id get clubbed inside the same object. Therefore, let’s write the code for this function −

Example

const arr = [
   {id: 1, h1: 'Daily tests'},
   {id: 2, h1: 'Details'},
   {id: 1, h2: 'Daily classes'},
   {id: 3, h2: 'Results'},
   {id: 2, h3: 'Admissions'},
   {id: 1, h4: 'Students'},
   {id: 2, h5: 'Alumni'},
   {id: 3, h3: 'Appreciations'},
   {id: 1, h5: 'Tiny Tots'},
   {id: 1, h6: 'Extras'},
];
const clubArray = (arr) => {
   return arr.reduce((acc, val, ind) => {
      const index = acc.findIndex(el => el.id === val.id);
      if(index !== -1){
         const key = Object.keys(val)[1];
         acc[index][key] = val[key];
      } else {
         acc.push(val);
      };
      return acc;
   }, []);
};
console.log(clubArray(arr));

Output

The output in the console will be −

[
   {
      id: 1,
      h1: 'Daily tests',
      h2: 'Daily classes',
      h4: 'Students',
      h5: 'Tiny Tots',
      h6: 'Extras'
   },
   { id: 2, h1: 'Details', h3: 'Admissions', h5: 'Alumni' },
   { id: 3, h2: 'Results', h3: 'Appreciations' }
]