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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: 24-Nov-2020
176 Views
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