TypeScript with Node.js: Backend Essentials Quiz Quiz

Explore the core concepts of using TypeScript in Node.js backend development. This quiz covers strongly typed programming, module systems, asynchronous handling, and effective project structure—all to ensure a robust TypeScript-based backend.

1. Type Safety in Request Handling

   When creating an API endpoint in a Node.js backend using TypeScript, which feature best helps catch mismatches in request parameters at compile time?

   1. Explicitly defining interface types for request objects
   2. Leaving parameters untyped for flexibility
   3. Using var to declare parameters
   4. Relying on JavaScript's dynamic typing

   Explanation: Defining interface types for request objects in TypeScript ensures that request parameters are correctly typed, allowing errors to be detected during compilation. JavaScript's dynamic typing does not enforce this, so mismatches would only appear at runtime. Declaring parameters with var does not provide type safety. Leaving parameters untyped removes the benefits of TypeScript's type checking.

2. Node.js Module Systems Compatibility

   Which TypeScript compiler setting ensures generated JavaScript code remains compatible with the CommonJS module system commonly used by Node.js?

   1. module: 'CommonJS'
   2. module: 'ES6'
   3. exportType: 'default'
   4. target: 'Node'

   Explanation: Setting the 'module' option to 'CommonJS' in your TypeScript configuration makes sure the output uses CommonJS syntax, which is compatible with Node.js. Choosing 'ES6' would use ES module syntax, which might not be compatible with all Node.js versions. The target option specifies JavaScript language version, not module system. The exportType setting is not a standard TypeScript option.

3. Error Handling in Asynchronous Controllers

   Given an asynchronous function in a TypeScript Node.js controller that fetches data from a database, what is the recommended way to handle errors?

   1. Use try-catch blocks within async functions
   2. Skip error handling and let unhandled rejections occur
   3. Always use the never type in return statements
   4. Wrap synchronous logic in setTimeout

   Explanation: Using try-catch blocks in async functions allows you to handle exceptions from awaited operations properly. Skipping error handling leads to unhandled promise rejections, which is unreliable. Wrapping synchronous logic in setTimeout does not help with error handling. Using the never type is unrelated to catching or managing errors.

4. Effective Project Structure

   Which practice helps keep a large TypeScript Node.js backend project maintainable as it grows?

   1. Mixing unrelated logic in shared files to reduce file count
   2. Organizing code with clear folder and module separation by feature
   3. Avoiding type definitions for simplicity
   4. Placing all code in a single main.ts file

   Explanation: Organizing code by feature—such as controllers, models, and services—makes the project easier to maintain, understand, and scale. Placing all code in a single file becomes unwieldy in large projects. Mixing unrelated logic complicates debugging and maintenance. Avoiding type definitions negates TypeScript's advantages and leads to more errors.

5. Transpiling TypeScript Code

   When running a TypeScript Node.js application in production, what is the standard approach for making TypeScript code executable by Node.js?

   1. Rename .ts files to .js files without transpiling
   2. Run TypeScript code directly without compilation
   3. Transpile TypeScript to JavaScript using the TypeScript compiler
   4. Use inline type annotations in comments only

   Explanation: Transpiling TypeScript to JavaScript with the TypeScript compiler generates plain JavaScript code that Node.js can execute. Running TypeScript code directly is not natively supported in Node.js environments. Renaming files without transpiling leaves TypeScript syntax and types in the code, which Node.js cannot interpret. Inline type annotations in comments are ignored by TypeScript and provide no runtime compatibility.