--- title: "TypeScript: Typed JavaScript Fundamentals" description: "Test your knowledge of TypeScript fundamentals with a quiz covering static typing, interfaces, generics, type guards, enums, classes, advanced types, and TypeScript best practices." author: "Mohammad Abu Mattar" canonical: https://mkabumattar.com/quizzes/post/typescript-fundamentals-quiz --- # TypeScript: Typed JavaScript Fundamentals Welcome to the TypeScript Basics Quiz! This quiz covers fundamental TypeScript concepts, static typing, and type-safe programming best practices. Each question is multiple-choice, and you'll find hints to help you along the way. Good luck! ## Questions ### 1. What is the primary purpose of TypeScript? - To increase the execution speed of the browser engine - To provide static type checking for JavaScript code - To eliminate the need for CSS and HTML in development - To automate the management of remote database servers **Hint:** It adds something JavaScript is missing. ### 2. Which command is used to compile a TypeScript file into JavaScript? - `npm start` - `tsc` - `node --compile` - `ts-build` **Hint:** TypeScript Compiler. ### 3. How do you define an interface for a User object? - `type User = { name: string; }` - `interface User { name: string; }` - `class User { name: string; }` - `struct User { name: string; }` **Hint:** Use the "interface" keyword. ### 4. What does the "any" type do? - It restricts a variable to only holding string data - It disables type checking for a particular variable - It allows a variable to be assigned only a null value - It creates a constant that cannot be changed later **Hint:** It turns off the safety features. ### 5. What is a "Tuple" in TypeScript? - An array that automatically grows as items are added - An array with a fixed number of elements and known types - A function that returns two different data types at once - A variable that can hold a string or a number selectively **Hint:** A list with a fixed number of elements and types. ### 6. Which keyword is used to make an interface property optional? - `!` - `?` - `void` - `null` **Hint:** The punctuation mark for a question. ### 7. What is an "Enum"? - A built-in method for encrypting sensitive string data - A collection of related and named constant numeric values - A specific type of loop used to iterate through objects - A function that executes itself immediately upon creation **Hint:** A set of named constants. ### 8. What does the "void" type signify when used on a function? - The function will terminate the program with an error - The function performs an action but returns no value - The function body has been left empty by the developer - The function is only accessible within its current class **Hint:** The function does its job but gives nothing back. ### 9. How do you define a Union Type in TypeScript? - `string & number` - `string | number` - `string + number` - `string [] number` **Hint:** The "pipe" symbol. ### 10. What is the "unknown" type? - A placeholder for variables that will be soon deprecated - A safer type that requires a type check before any usage - A type used to represent variables that have been deleted - A specialized type for handling error objects in catches **Hint:** A safer version of "any". ### 11. What is the purpose of the "readonly" keyword? - To ensure a property cannot be accessed by outside files - To prevent a property from being changed after assignment - To optimize the loading speed of large data structures - To mark a variable for inclusion in the browser storage **Hint:** It prevents changes. ### 12. What is "Generics" in TypeScript? - A library of pre-written functions for common web tasks - A way to create components that work with a variety of types - A tool for generating random data for testing applications - A method for translating TypeScript into different languages **Hint:** Creating components that work over a variety of types. ### 13. Which file contains the configuration for a TypeScript project? - `package.json` - `tsconfig.json` - `typescript.json` - `.ts-settings` **Hint:** ts-config. ### 14. What is "Type Inference"? - When a developer explicitly defines a variable as a string - When the compiler automatically detects a variable type - A technique for forcing one data type into another type - A process for removing all type information from a file **Hint:** TypeScript guessing the type. ### 15. What is the "never" type used for? - For variables that are initialized with a null value - For functions that do not reach an end point or return - For components that are not intended to be reused - For code that is executed only during the testing phase **Hint:** For values that will never occur. ### 16. How do you extend an interface? - `interface Admin + User` - `interface Admin extends User` - `interface Admin : User` - `interface Admin is User` **Hint:** Use the "extends" keyword. ### 17. What is an "Abstract Class"? - A class that is hidden from other modules in the project - A base class that cannot be instantiated directly - A class that only contains static methods and constants - A class designed to represent visual shapes in a UI **Hint:** A class that cannot be instantiated on its own. ### 18. Which keyword is used to access the parent class constructor? - `parent()` - `super()` - `base()` - `this.constructor()` **Hint:** Think "Super". ### 19. What is a "Type Guard"? - A security mechanism that prevents unauthorized code access - A check that narrows a type within a specific scope - A function that validates that a user is logged in - A variable that stores the current state of an interface **Hint:** It narrows down a type within a block of code. ### 20. What is the "as" keyword used for? - `To rename a variable for use in a different file` - `To tell the compiler to treat a value as a specific type` - `To import a specific module into the global scope` - `To create a loop that iterates through an array` **Hint:** Type Assertion. ### 21. What is the result of transpiling TypeScript to JavaScript? - A compressed file that executes faster in the browser - A standard JavaScript file with all types removed - An encrypted file that is unreadable to human developers - A binary file that runs directly on the server hardware **Hint:** The types disappear. ### 22. How do you declare a private property in a TypeScript class? - `hidden name: string;` - `private name: string;` - `#name: string;` - `internal name: string;` **Hint:** The "private" keyword. ### 23. What is "Literal Types"? - A type that allows any string or number to be stored - A type that can only hold a specific, exact value - A type used for documentation in large-scale projects - A type that can be changed by the user at runtime **Hint:** The type is a specific value. ### 24. What is "Intersection Type"? - A type that can be one of several different types - A type that combines multiple types into a single one - A type that is used to connect two separate databases - A type that prevents a function from being executed **Hint:** Combining multiple types into one. ### 25. What is the "protected" modifier? - It makes the property accessible to everyone globally - It makes properties visible to a class and its children - It encrypts the property so it cannot be viewed in JS - It prevents the property from being deleted or removed **Hint:** Visible to the family. ### 26. How do you define a function type in an interface? - `myFunc: void;` - `myFunc(): void;` - `function myFunc(): void;` - `def myFunc(): void;` **Hint:** name(params): returnType ### 27. What is "Namespace" in TypeScript? - A way to organize files within the operating system - A way to group related code and prevent collisions - The specific URL where your project is hosted online - A specialized database for storing key-value pairs **Hint:** Grouping related code. ### 28. What is the "keyof" operator? - It checks if a specific key is present in an object - It creates a union type of all keys from an object type - It renames the primary key of a database table record - It exposes a variable that was marked as private **Hint:** It extracts the keys. ### 29. What does "Strict Mode" in tsconfig do? - It prevents the code from running on mobile browsers - It enables comprehensive checks for more reliable code - It forces all variable names to be written in all caps - It automatically deletes code that contains any errors **Hint:** It makes the compiler very picky. ### 30. What is the "!" operator (Non-null assertion)? - It indicates that a variable is not used in the file - It asserts that a value is not null or undefined - It triggers an immediate error if a variable is empty - It makes a variable available to all other functions **Hint:** You are telling the compiler: "Trust me, it exists".