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Hands-On-Functional-Programming-with-Typescript

Hands-On Functional Programming with Typescript, published by Packt

How to run the examples?

To be able to run the examples, you first need to install all the required dependencies using the following command:

npm install

You will also need to install TypeScript and ts-node as global dependencies:

npm install -g typescript ts-node

You can then run then run an example using the ts-node command:

ts-node chapters/chapter_01_fp_fundamentals/01_pure_vs_inpure.ts

The code examples use a namespace for each demo to prevent conflicts between variables declared in multiple examples. In real-world TypeScript applications using namespaces (AKA internal modules) is discouraged and ES6 modules should be the preferred option instead.

Please note that some examples such as the ones in the 01_pure_vs_inpure.ts file will not display anything in the terminal, which is normal because now functions are invoked in the case.

Also, the examples in 01_pure_vs_inpure.ts use window.location so we would need to invoke the function in a web browser, not in Node.js.

The best option for this case is to copy the example in the TypeScript Playground. We can copy the code in the playground (left) to get the resulting JavaScript output (right)

It is also important to enable all the TypeScript strict features in the playground:

We can then execute the resulting JavaScript code in the console in the developer tools of our web browser:

The TypeScript playground and the browser console are the recommended way to execute examples that use APIs that are only available in web browsers such as the DOM and BOM APIs. It is recommended to use the ts-node command or all other examples.

ts-node chapters/chapter_01_fp_fundamentals/02_side_effects.ts

All the examples are designed so you can experiment with them and learn by yourself. In the case of the examples in the 01_pure_vs_inpure.ts file, you will have to add some additional code to see potential effects. You can invoke one function at a time to get a better idea of what is going on.

Some examples will fail at compilation time or runtime time to showcase how the compiler can detect specific errors. All the errors that are meant to happen on propose have been annotated with a commend // Error.

Code examples