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

In TypeScript, you can use the map function from the Underscore library by first importing Underscore and then calling the map function on an array.

Here is an example of using the map function in TypeScript with type annotations:

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

// Array of numbers
const numbers: number[] = [1, 2, 3, 4];

// Use the map function to double each number in the array
const doubledNumbers: number[] = _.map<number, number>(numbers, (num: number) => {
  return num * 2;
});

console.log(doubledNumbers); // [2, 4, 6, 8]
305 chars
12 lines

The _.map function takes two arguments: the array to iterate over, and a callback function that will be called for each element in the array. The callback function should accept one argument, which will be the current element, and should return the transformed element.

Type annotations are used to specify the generic types of the _.map function. In this example, we are specifying that the input array is an array of numbers, and that the output array will also be an array of numbers.

This demonstrates how to use the map function from the Underscore library in TypeScript, as well as the use of type annotations for ensuring type safety.