TypeScript Interview Questions

1.      What is TypeScript and what are its main features?

TypeScript is a superset of JavaScript that adds optional static typing, classes, interfaces, and other features to the language. It allows developers to write more maintainable and scalable code.

2.      What is the difference between TypeScript and JavaScript?

TypeScript is a superset of JavaScript, which means that any valid JavaScript code is also valid TypeScript code. The main difference is that TypeScript adds optional static typing, classes, interfaces, and other features to the language.

3.      What are the benefits of using TypeScript?

The benefits of using TypeScript include: improved code quality and maintainability, better tooling and editor support, improved type checking and error handling, and improved scalability.

4.      How does TypeScript handle type checking?

TypeScript uses a technique called "duck typing" to check the types of variables, which means that it checks the shape of an object rather than its class or interface.

5.      What is the difference between a type and an interface in TypeScript?

A type in TypeScript is a way to describe the shape of an object, whereas an interface is a way to describe the shape of an object in a more formal and explicit way.

6.      What is a decorator in TypeScript?

A decorator is a way to add metadata to a class, method, or property in TypeScript. Decorators are used to add functionality to a class, such as adding an element to the DOM or logging method calls.

7.      What is a tuple in TypeScript?

A tuple is a way to describe an array with a fixed number of elements and specific types.

8.      What is a union type in TypeScript?

A union type is a way to describe a value that can have one of several types.

9.      What is a type alias in TypeScript?

A type alias is a way to give a name to a type.

10.   How can you use TypeScript with Node.js?

TypeScript can be used with Node.js by transpiling the TypeScript code to JavaScript using the TypeScript compiler, and then running the generated JavaScript code using Node.js.

11.   How does TypeScript handle backward compatibility with JavaScript?

TypeScript is designed to be backward compatible with JavaScript, which means that you can use TypeScript code in JavaScript projects and vice versa. TypeScript also allows you to use JavaScript libraries and frameworks in TypeScript projects.

12.   What is the difference between a class and an interface in TypeScript?

A class is a blueprint for creating objects, it can include properties, methods, and constructors, whereas an interface is a way to describe the structure of an object, it can include properties and methods, but it cannot include constructors.

13.   How can you use TypeScript with Angular?

TypeScript is fully integrated with Angular and it is the recommended language for developing Angular applications. You can use TypeScript by configuring the project to use TypeScript and then writing the code using TypeScript syntax.

14.   What is the role of the TypeScript compiler?

The TypeScript compiler is responsible for converting TypeScript code into JavaScript code, it also performs type checking and generates error messages if there are any type errors.

15.   What is a namespace in TypeScript?

A namespace is a way to organize code and prevent naming conflicts. It allows you to group related classes, interfaces, and functions under a single name.

16.   What is a type assertion in TypeScript?

A type assertion is a way to tell the TypeScript compiler that a value has a certain type, even if the type cannot be inferred from the value.

17.   What is a type guard in TypeScript?

A type guard is a way to check the type of a value

18.   How can you use TypeScript with React?

TypeScript can be used with React by adding the @types/react package to the project, which includes the TypeScript definitions for React. You can then write React components using TypeScript syntax.

19.   What is a mapped type in TypeScript?

A mapped type is a way to create a new type by applying a transformation to the properties of an existing type. It allows you to create new types based on existing types.

20.   What is a discriminated union in TypeScript?

A discriminated union is a way to create a type that can have one of several types, but each type has a unique property that can be used to determine the type.

21.   How can you use TypeScript with webpack?

TypeScript can be used with webpack by adding the ts-loader package to the project, which allows webpack to transpile TypeScript code to JavaScript.

22.   What is a type parameter in TypeScript?

A type parameter is a way to create a generic type that can work with different types. It allows you to create a type that can be used with multiple types.

23.   What is a type inference in TypeScript?

Type inference is the process of determining the type of a value based on the context in which it is used. TypeScript uses type inference to infer the types of variables and parameters.

24.   What is a type predicate in TypeScript?

A type predicate is a way to test the type of a value. It allows you to test if a value is of a certain type.

25.   What is a type alias in TypeScript?

A type alias is a way to give a name to a type. It allows you to create a new name for a type, which can make the code more readable.

26.   What is a type union in TypeScript?

A type union is a way to specify that a variable can have one of several types. It allows you to define a variable that can be of multiple types.

27.   How can you use TypeScript with Express?

TypeScript can be used with Express by installing the @types/express package, which includes the TypeScript definitions for Express. Then you can use Express with TypeScript by writing the Express code using TypeScript syntax.

28.   How can you use TypeScript with MongoDB?

TypeScript can be used with MongoDB by installing the @types/mongodb package, which includes the TypeScript definitions for MongoDB. Then you can use MongoDB with TypeScript by writing the MongoDB code using TypeScript syntax.

29.   What is a type literal in TypeScript?

A type literal is a way to create a type that has a fixed set of properties and values. It allows you to create a type that can only have specific properties and values.

30.   How can you use TypeScript with GraphQL?

TypeScript can be used with GraphQL by installing the @graphql-codegen/typescript package, which can generate TypeScript types from GraphQL schema.