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

To use the isString function from the Underscore library in TypeScript, you need to install the Underscore library and its type definitions using npm. Type definitions provide the necessary types for TypeScript to properly check and validate the usage of the Underscore library functions.

You can install Underscore and its type definitions using the following command:

npm install underscore @types/underscore

Once installed, you can import the isString function and use it in your TypeScript code as follows:

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

const str = "Hello, World!";
if (_.isString(str)) {
  console.log("The variable str is a string.");
} else {
  console.log("The variable str is not a string.");
}
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In this code, we first import the underscore module as _. Then, we define a string str. We use the isString() function from the _ object to check if str is a string. If it is, we print a message indicating that str is a string. Otherwise, we print a message indicating that it is not a string.

By installing the Underscore library and its type definitions and using them as shown, the TypeScript compiler will properly check the types of str and the result of calling isString(), ensuring that your program is type-safe.