Learn RxJS page

Learn RxJS by creating a validating credit card form.

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In this tutorial we will create the following validating credit card form:

See the Pen Angular + RXJS by Justin Meyer (@justinbmeyer) on CodePen.

This credit card form:

  • Validates input as a user types, but only once a user blurs an input element.
  • Enables the PAY button once the credit card information is valid.
  • Disables the PAY button and changes its text to PAYING while payment is being processed.
  • Logs a success message when payment has completed.
  • Simulates a payment with a Promise that resolves in 2 seconds.

We will use RxJS 7.4 and Angular 12 for this example. All code examples will be able to work in a CodePen so you just need a browser to complete this tutorial!

Each section of the guide is broken down into the following sections:

  • The problem — A description of what the section is trying to accomplish.
  • What you need to know — Information that is useful for solving the problem.
  • The solution — The solution to the problem.


Logic Flow

The following presentation shows how the observables are wired up. This will be a useful reference for understanding how the tutorial works:


  • Open Developer Tools and stack CodePen vertically:

    CodePen stacked

  • Save your CodePen

  • If you can’t figure out what is breaking, use an online diff checker to compare your code with the solution.

    Diff Checker


  • This guide makes a minor use of promises. A basic understanding of promises is required.
  • This guide makes a minor use of TypeScript. TypeScript knowledge is not required, but it might help to make sense of the solutions. The Learn TypeScript guide is more than sufficient background.
  • This guide uses Angular. However, most of the Angular parts are explained. Angular experience is not required; however, experience in some other modern web framework is required.

Next steps

Head over to the first lesson and learn about observables.