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

To use the constant function from the Underscore library in TypeScript, you can include the Underscore library and its type definitions in your project.

Here is an example:

1. Install Underscore and its type definitions:

index.ts
npm install underscore --save
npm install @types/underscore --save-dev
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2. Import the constant function and use it as follows:

index.ts
import { constant } from "underscore";

// define a function that always returns 0
const alwaysZero = constant(0);

// usage example
console.log(alwaysZero()); // output: 0
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The constant function returns a function that always returns the same value. In the example above, we defined a function alwaysZero that always returns 0.

Note that in TypeScript, you can also define the type of the returned function using a type alias or an interface:

index.ts
type NumberFunc = () => number;

const alwaysZero: NumberFunc = constant(0);
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This defines a type alias NumberFunc for a function that takes no arguments and returns a number. We then use this type alias to define the type of the alwaysZero function.