Module formats

Modules feature in JavaScript as part of ES6, which is great. However, lots of code exists in other popular module formats that came before this standardization. TypeScript allows us to write our code using ES6 modules, which can then transpile into another module format if specified.

Here is a brief description of the different module formats that TypeScript can transpile to:

• Asynchronous Module Definition (AMD): This is commonly used in code targeted for the browser and uses a define function to define modules.
• CommonJS: This format is used in Node.js programs. It uses module.exports to define modules and require to define dependencies.
• Universal Module Definition (UMD): This can be used in both browser apps and Node.js programs.
• ES6: This is the native JavaScript module format and uses the export keyword to define modules and import to define dependencies.

In the following sections (and, in fact, this whole book), we'll write our code using ES6 modules.