Convert 2D Tabular Data into Array of Objects in JavaScript

Suppose, we have an array of arrays like this −

const arr = [
   ["Ashley","2017-01-10",80],
   ["Ashley","2017-02-10",75],
   ["Ashley","2017-03-10",85],
    ["Clara","2017-01-10",90],
   ["Clara","2017-02-10",82]
];

We are required to write a JavaScript function that takes in one such array as the first and the only input.

The function should then construct a new array of objects based on the input array. The array should contain an object for each unique subarray of the input array. (by unique, in this context, we mean the subarray that have their first element unique).

Each object must have the following schema −

const output = [
   {"name":"Ashley", "2017-01-10":80, "2017-02-10":75, "2017-03-10":85},
   {"name":"Clara", "2017-01-10":90, "2017-02-10":82}
];

Example

const arr = [
   ["Ashley","2017-01-10",80],
   ["Ashley","2017-02-10",75],
   ["Ashley","2017-03-10",85],
   ["Clara","2017-01-10",90],
   ["Clara","2017-02-10",82]
];
const groupArray = (arr = []) => {
   let grouped = [];
   grouped = arr.reduce(function (hash) { return function (r, a) {
      if (!hash[a[0]]) {
         hash[a[0]] = {
            name: a[0] };
            r.push(hash[a[0]]);
      }
      hash[a[0]][a[1]] = a[2];
      return r;
   };
}
(Object.create(null)), []);
   return grouped;
}
console.log(groupArray(arr));

Output

And the output in the console will be −

[
   { name: 'Ashley',
   '2017-01-10': 80,
   '2017-02-10': 75,
   '2017-03-10': 85
   },
   { name: 'Clara',
   '2017-01-10': 90,
   '2017-02-10': 82 }
]