Syntax error Grouping an Array and Counting items creating new array based on Groups in JavaScript

Grouping an Array and Counting items creating new array based on Groups in JavaScript

Suppose, we have an array of objects like this −

const arr = [
   { region: "Africa", fruit: "Orange", user: "Gary" },
   { region: "Africa", fruit: "Apple", user: "Steve" },
   { region: "Europe", fruit: "Orange", user: "John" },
   { region: "Europe", fruit: "Apple", user: "bob" },
   { region: "Asia", fruit: "Orange", user: "Ian" },
   { region: "Asia", fruit: "Apple", user: "Angelo" },
   { region: "Africa", fruit: "Orange", user: "Gary" }
];

We are required to write a JavaScript function that takes in one such array. The function should prepare a new array of objects that groups the data based on the "area" property of objects.

The function should also keep a count of the unique users for a particular area.

Therefore, for the above array, the output should look like −

const output = [
   {
      "region": "Africa",
      "count": 2
   },
   {
      "region": "Europe",
      "count": 2
   },
   {
      "region": "Asia",
      "count": 2
   }
];

Example

The code for this will be −

const arr = [
   { region: "Africa", fruit: "Orange", user: "Gary" },
   { region: "Africa", fruit: "Apple", user: "Steve" },
   { region: "Europe", fruit: "Orange", user: "John" },
   { region: "Europe", fruit: "Apple", user: "bob" },
   { region: "Asia", fruit: "Orange", user: "Ian" },
   { region: "Asia", fruit: "Apple", user: "Angelo" },
   { region: "Africa", fruit: "Orange", user: "Gary" }
];
const groupByArea = (arr = []) => {
   const res = [];
   arr.forEach(el => {
      let key = [el.region, el.user].join('|');
      if (!this[el.region]) {
         this[el.region] = { region: el.region, count: 0 };
         res.push(this[el.region]);
      };
      if (!this[key]) {
         this[key] = true;
         this[el.region].count++;
      };
   }, Object.create(null));
   return res;
}
console.log(groupByArea(arr));

Output

And the output in the console will be −

[
   { region: 'Africa', count: 2 },
   { region: 'Europe', count: 2 },
   { region: 'Asia', count: 2 }
]
Updated on: 2020-11-24T10:17:54+05:30

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