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

To use the object functions from the Underscore library in TypeScript, you need to first install the dependencies: Underscore and its TypeScript definitions. You can do this using npm as follows:

npm install underscore
npm install --save-dev @types/underscore
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After installing the dependencies, you can import the library and use its functions as follows:

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

const obj = { one: 1, two: 2, three: 3, four: 4 };
const newObj = _.object(_.map(_.pairs(obj), (pair) => [pair[0].toUpperCase(), pair[1] * 2]));
console.log(newObj); // {ONE: 2, TWO: 4, THREE: 6, FOUR: 8}
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In the example above, we first imported the Underscore library using import * as _ from 'underscore'. Then, we defined an object obj with some key-value pairs. We used the _.object function to create a new object with keys converted to uppercase and values multiplied by 2. To achieve this, we first used the _.pairs function to convert the original object into an array of key-value pairs, then we used the _.map function to map each pair into a new array with the uppercase key and the multiplied value. Finally, we passed the result of the mapping to the _.object function to create the new object.

Note that TypeScript provides type annotations for the Underscore library, which can improve code readability and help catch type-related errors at compile-time. For example, you can annotate the input and output types of the _.object function as follows:

index.ts
interface KeyValuePair<T> {
  [key: string]: T;
}

function object<T>(list: [string, T][]): KeyValuePair<T> {
  // implementation
}
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This interface declares a generic type T and describes an object with string keys and values of type T. The object function takes an array of tuples where the first element is a string key and the second element is a value of type T. The function returns an object with the same keys and type T values.