How to use external plain JavaScript libraries in TypeScript?

To use external plain JavaScript libraries in TypeScript, you can follow several steps to ensure that the library integrates smoothly with your TypeScript project. This process involves handling type definitions to take advantage of TypeScript's type-checking capabilities. Here's a comprehensive approach:

1. Search for Type Definitions: The first step is to check if the JavaScript library you're planning to use has TypeScript type definitions available. These type definitions, or .d.ts files, provide TypeScript with information about the types within the JavaScript library. You can search for these on DefinitelyTyped, a large repository of high-quality TypeScript type definitions, or check if the library itself includes type definitions[1][2].

2. Install Type Definitions: If type definitions are available, you can install them using npm. For libraries included in DefinitelyTyped, the type definitions can be installed with a command like npm install @types/library_name --save-dev. This command adds the type definitions as a development dependency in your project[1][2].

3. Manual Type Definitions: If no type definitions are available for the library, you have the option to create them manually. This involves creating a .d.ts file where you declare the types for the library's API. For example, you can start by declaring a module and then define the types for the library's functions and variables[3].

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   // Example of a custom type definition file (custom_library.d.ts)
   declare module 'custom_library' {
       export function someFunction(arg: string): void;
   }

4. Using the declare Keyword for Quick Fixes: For a quick and dirty solution, especially when you're just experimenting or the library usage is minimal, you can use the declare keyword to tell TypeScript to treat the library or any of its components as any type. This approach bypasses type checking for the library, which is not recommended for production code but can be useful for prototyping[1].

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   declare var libraryGlobal: any;

5. Configuration in tsconfig.json: Ensure your tsconfig.json file is correctly configured to include the .d.ts files. If you're using custom type definitions, make sure they are located in a directory that is included in your TypeScript project's compilation context[2].

6. Importing and Using the Library: Once the type definitions are in place, ...