how to use the identity function from the underscore library in javascript

The identity function from the Underscore library simply returns its first argument. This function can be useful as a default for a higher-order function that expects a function as an argument, but the actual operation is not critical.

Here's an example illustrating the use of the identity function in JavaScript:

index.tsx
const _ = require('underscore');

const nums = [1, 2, 3, 4];
const result = _.map(nums, _.identity); 

console.log(result); // [1, 2, 3, 4]
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In this code, we use the require() function to import the Underscore library. We then define an array of numbers called nums. Finally, we call the map() function from Underscore, passing in nums as the array to map, and _.identity as the function to apply. The result is that each element in nums is returned unchanged, creating a new array with the same values.