TypeScript:
Using an interactive shell (REPL)
How to:
TypeScript doesn’t come with its own REPL. Let’s use ts-node, a TypeScript execution environment for Node.js that includes a REPL.
First, install it globally:
npm install -g ts-nodeStart the REPL by typing ts-node in your command line:
ts-nodeHere’s a quick snippet to try:
> let message: string = 'Hello, REPL!';
> console.log(message);
Hello, REPL!
>
To end the session, press Ctrl+D.
Deep Dive
Historically, REPLs were prominent in languages like Lisp, allowing for dynamic code evaluation. The concept has since spread, becoming a staple for interactive coding in many languages.
For TypeScript, ts-node isn’t your only option. Alternatives include using the TypeScript Playground in a web browser or leveraging other Node.js-based REPLs that support TypeScript with suitable plugins.
In terms of implementation, ts-node uses the TypeScript compiler API to transpile code on-the-fly before it is executed by Node.js. This gives you immediate feedback and is particularly useful for trying out TypeScript’s latest features without setup hassles.
One thing to remember – while a REPL is great for quick tests, it doesn’t replace writing traditional, testable, and maintainable code. It’s a tool for learning and exploration, not a substitute for proper development practices.