how to use the groupby function from the underscore library in typescript

To use the groupBy function from the Underscore library in TypeScript, you can import the library and apply the function to a collection of objects. Here's an example:

index.ts
import * as _ from 'underscore';

interface Person {
  name: string;
  age: number;
}

const people: Person[] = [
  { name: 'Alice', age: 25 },
  { name: 'Bob', age: 30 },
  { name: 'Charlie', age: 25 },
];

const groupedPeople = _.groupBy(people, 'age');

console.log(groupedPeople);
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In this example, we first define an interface for a Person, which has a name and an age. We then define an array of Person objects called people.

To group these people by age using the groupBy function from Underscore, we pass in the people array along with the property name 'age' as the second argument.

The result of this function call is an object where the keys are the distinct values of the 'age' property and the values are arrays of Person objects that have that age.

In this example, the groupedPeople object looks like this:

index.tsx
{
  '25': [
    { name: 'Alice', age: 25 },
    { name: 'Charlie', age: 25 },
  ],
  '30': [
    { name: 'Bob', age: 30 },
  ],
}
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This demonstrates how to use the groupBy function from Underscore in TypeScript to group a collection of objects.