How to distinguish a framework from a library and what are the key differences between them?

A framework and a library are tools for development, but they differ in their principles of code management.

Key differences:

• Flow control:

  • Library provides a set of functions or classes that the developer calls as needed. Control over the program flow remains with the developer.
  • Framework defines the structure of the application and manages calls to the developer’s code (inversion of control). The developer inserts their code into specific points of the framework.

• Scope of application:

  • Libraries typically solve specific tasks (e.g., working with dates, HTTP requests).
  • Frameworks provide a skeleton for building the entire application (e.g., Express.js for Node.js).

• Example:

  • Using the lodash library for working with arrays — you call the functions yourself.
  • Using the Express framework — you create handlers, and the framework manages routing and server startup.

Thus, the main difference is who controls the flow of execution: you (library) or the framework (inversion of control).