Are you a software developer preparing for your TypeScript interview? Don’t worry; our guide is here to help you! We have researched and compiled a list of the 15+ most commonly asked TypeScript interview questions.
And guess what? You’ll also get answers to these questions along with practice interview tips.
So, let’s begin!
What is TypeScript?
TypeScript is an open-source programming language developed by Microsoft. It is a syntactical superset of JavaScript that introduces optional static typing.
This programming language compiles down to JavaScript and is particularly suited for developing large-scale applications.
Demand for TypeScript Developers
According to Statista’s 2023 report, TypeScript is among the top 5 most used programming languages among developers.
Here’s a fun fact,
Around 38.87% of software developers prefer using TypeScript for their projects.
And guess what?
It is used by some of the top tech companies around the world, like Meta, Microsoft, Opera, and NASA.
Moreover, TypeScript is one of the most in-demand programming languages in India. IT companies in India are actively looking for developers proficient in these programming languages.
Don’t believe us?
Visit Hirist and see for yourself. There are tens and hundreds of TypeScript jobs listed on this online IT job portal.
TypeScript Basic Interview Questions
Here are the most common TypeScript interview questions and answers for freshers.
- What are the key benefits of using TypeScript?
TypeScript offers several advantages:
- Enhanced code quality and maintainability with static typing.
- Early detection of errors during development due to static type checking.
- Improved tooling and IDE support for code navigation and refactoring.
- Ability to use modern JavaScript features and compile down to older versions for broader compatibility.
- How do you install TypeScript?
TypeScript can be installed globally via npm using the command:
npm install -g TypeScript
This installs the TypeScript compiler (tsc) globally, allowing you to compile TypeScript files from the command line.
- What is a TypeScript interface?
An interface in TypeScript defines the structure of an object by specifying properties and their types.
It provides a way to define contracts within your code and is purely used for type-checking purposes at compile-time.
- How do you compile TypeScript code?
TypeScript code can be compiled into JavaScript using the TypeScript compiler (tsc).
You can compile a TypeScript file (e.g., filename.ts) to JavaScript by running the command:
tsc filename.ts
This generates a corresponding JavaScript file (filename.js) based on the TypeScript code.
- What is type inference in TypeScript?
Type inference is TypeScript’s ability to automatically deduce the type of a variable based on its initialization value.
This allows developers to write cleaner code by omitting explicit type annotations while still benefiting from static typing.
Also Read - Top 25+ JavaScript Interview Questions and Answers
TypeScript Interview Questions For Experienced
Here are the commonly asked TypeScript interview questions and answers for experienced candidates.
- Explain the concept of static typing in TypeScript. How does it benefit software development?
Static typing in TypeScript refers to the ability to specify types for variables and parameters and return values at compile time.
This helps detect type-related errors early in the development process, leading to more robust and maintainable code.
Static typing enhances code quality by providing better tooling support and improved developer experience.
- What are generics in TypeScript? Provide an example of how you would use generics in a TypeScript project.
Generics in TypeScript allow you to create reusable components and functions that work with a variety of types.
For example:
function identity<T>(arg: T): T {
return arg;
}
let result = identity<string>(“Hello”);
- What are decorators in TypeScript? How can decorators be used to enhance a class or method?
Decorators are a TypeScript feature used to add metadata or modify the behaviour of classes, methods, or properties at design time.
They are typically used in frameworks like Angular for features like dependency injection, route handling, and more.
- Explain the concept of access modifiers (public, private, protected) in TypeScript. Provide an example of how each modifier is used.
Access modifiers control the visibility and accessibility of class members in TypeScript.
- public: Accessible from anywhere.
- private: Accessible only within the class.
- protected: Accessible within the class and its subclasses.
Example:
class Person {
private name: string;
constructor(name: string) {
this.name = name;
}
}
- What is the role of TypeScript declaration files (.d.ts)? When would you use them in a project?
TypeScript declaration files (*.d.ts) provide type definitions for existing JavaScript libraries or modules that don’t have TypeScript support.
They allow TypeScript to understand the shape and types of external libraries, enabling better type checking and IDE support.
Advanced TypeScript Interview Questions
Here are some advanced TypeScript interview questions and answers.
- What are mapped types in TypeScript? Provide an example of how you would use a mapped type.
Mapped types in TypeScript allow you to create new types based on the properties of an existing type. They use key remapping via conditional types.
For example:
type Person = {
name: string;
age: number;
};
type ReadonlyPerson = {
readonly [K in keyof Person]: Person[K];
};
const person: ReadonlyPerson = { name: “John”, age: 30 };
// Now ‘person’ properties are readonly
- Explain the concept of conditional module loading using TypeScript. How can you implement conditional imports based on environment variables?
Conditional module loading in TypeScript allows you to import modules dynamically based on runtime conditions.
You can use techniques like dynamic import statements (import()), which return a promise and can be conditionally executed based on environment variables or other runtime parameters.
- Explain conditional types in TypeScript. How can conditional types be useful in writing generic code?
Conditional types in TypeScript use type conditions to determine the resulting type based on a condition.
They are often used in generic types to create flexible type definitions that adapt based on runtime values.
For example:
type Check<T> = T extends string ? “String Type”: “Non-String Type”;
type Result = Check<string>; // Result is “String Type”
type AnotherResult = Check<number>; // Result is “Non-String Type”
TypeScript Coding Questions
Here are the most important TypeScript coding questions and answers.
- Implement a function to calculate the factorial of a number using TypeScript.
function factorial(n: number): number {
if (n === 0 || n === 1) {
return 1;
} else {
return n * factorial(n – 1);
}
}
// Example usage:
console.log(factorial(5)); // Output: 120
- Implement a TypeScript class representing a basic calculator with add, subtract, multiply, and divide methods.
class Calculator {
add(a: number, b: number): number {
return a + b;
}
subtract(a: number, b: number): number {
return a – b;
}
multiply(a: number, b: number): number {
return a * b;
}
divide(a: number, b: number): number {
if (b === 0) {
throw new Error(‘Cannot divide by zero’);
}
return a / b;
}
}
// Example usage:
const calc = new Calculator();
console.log(calc.add(5, 3)); // Output: 8
console.log(calc.multiply(4, 2)); // Output: 8
- Write a TypeScript function to remove duplicate elements from an array while preserving the original order.
function removeDuplicates<T>(arr: T[]): T[] {
return arr.filter((value, index, self) => self.indexOf(value) === index);
}
// Example usage:
const numbers = [1, 2, 3, 2, 4, 3, 5];
const uniqueNumbers = removeDuplicates(numbers);
console.log(uniqueNumbers); // Output: [1, 2, 3, 4, 5]
Angular TypeScript Interview Questions
Learn these commonly asked Angular TypeScript questions with answers.
- What is Angular, and how does TypeScript play a role in Angular development?
Angular is a popular front-end web framework developed by Google. TypeScript is the primary language used for Angular development.
Angular leverages TypeScript’s features like static typing, classes, decorators, and interfaces to build robust, scalable, and maintainable web applications.
- What is Angular CLI (Command Line Interface), and how do you use it for Angular development?
Angular CLI is a command-line tool used for initializing, developing, scaffolding, and maintaining Angular applications.
You can use Angular CLI to create new projects, generate components, services, modules, and more, and run development servers and production builds.
Also Read - Top 25+ Frontend Interview Questions and Answers
React TypeScript Interview Questions
Here are some important React TypeScript questions, along with their answers.
- What is the advantage of using TypeScript with React?
TypeScript enhances React development by adding static typing, which helps catch errors early in the development process.
It improves code quality, provides better tooling support (e.g., IntelliSense), and makes large-scale React applications more maintainable and scalable.
- How do you handle events in React components using TypeScript? Provide an example.
Event handlers in React components can be typed using TypeScript.
For example:
const MyButton: React.FC = () => {
const handleClick = (event: React.MouseEvent<HTMLButtonElement>) => {
console.log(‘Button clicked’);
};
return <button onClick={handleClick}>Click Me</button>;
};
Also Read - Top 25+ React JS Interview Questions and Answers
Tips to Answer TypeScript Interview Questions
Here are some tips you can follow when answering the interview questions.
- Keep your answers simple and to the point.
- Use examples to explain TypeScript concepts clearly.
- Highlight how TypeScript helps in writing better code.
- Relate TypeScript concepts to real-world applications and projects.
- Show confidence in your knowledge and approach when answering questions.
Wrapping Up
So, here are the top 15+ TypeScript interview questions and answers to help you prepare for your next interview in software development. Practice these answers with confidence to showcase your skills. Looking for TypeScript jobs? Explore opportunities on Hirist, the leading IT job portal in India. Find TypeScript jobs on Hirist for your next career move!