Interview Questions and Answers
Freshers / Beginner level questions & answers
Ques 1. What is TypeScript?
TypeScript is a superset of JavaScript that adds static typing and other features to the language.
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Ques 2. Explain the difference between 'let' and 'const' in TypeScript.
'let' is used to declare variables with block scope, while 'const' is used to declare constants with block scope that cannot be reassigned.
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Ques 3. What are the basic data types in TypeScript?
The basic data types in TypeScript are number, string, boolean, null, undefined, and object.
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Ques 4. How do you define an interface in TypeScript?
Interfaces in TypeScript are defined using the 'interface' keyword, followed by the interface name and a set of property declarations.
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Ques 5. What is the 'any' type in TypeScript?
The 'any' type in TypeScript is used to represent a dynamic type that can hold values of any type, and it bypasses type checking.
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Ques 6. How do you declare an array in TypeScript?
Arrays in TypeScript can be declared using the syntax 'let myArray: number[] = [1, 2, 3];' or 'let myArray: Array
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Ques 7. How do you handle errors in TypeScript?
Errors in TypeScript can be handled using try-catch blocks, similar to JavaScript.
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Ques 8. How do you use optional parameters in TypeScript?
Optional parameters in TypeScript are denoted by adding a '?' after the parameter name in the function declaration.
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Ques 9. What is the 'readonly' modifier in TypeScript?
The 'readonly' modifier in TypeScript is used to make properties of an object immutable after their initial assignment.
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Ques 10. Explain the concept of union types in TypeScript.
Union types in TypeScript allow a variable to hold values of multiple types, separated by the '|' symbol.
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Ques 11. How do you declare and use a class in TypeScript?
Classes in TypeScript are declared using the 'class' keyword, and objects are created using the 'new' keyword.
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Ques 12. What is the 'for...of' loop in TypeScript?
The 'for...of' loop in TypeScript is used to iterate over the values of an iterable object, such as an array or a string.
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Ques 13. How do you use the 'import' statement in TypeScript?
The 'import' statement in TypeScript is used to import modules or exports from other files.
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Ques 14. How do you use the 'in' operator in TypeScript?
The 'in' operator in TypeScript is used to check if a property exists in an object.
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Ques 15. What is the 'Tuple' type in TypeScript?
A tuple in TypeScript is a fixed-size, ordered list of elements where each element can have a different type.
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Ques 16. What is the purpose of the 'export' keyword in TypeScript?
The 'export' keyword in TypeScript is used to make functions, variables, or classes available for use in other files by importing them.
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Intermediate / 1 to 5 years experienced level questions & answers
Ques 17. Explain the concept of static typing in TypeScript.
Static typing in TypeScript involves specifying the data types of variables at compile time, which helps catch type-related errors early in the development process.
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Ques 18. Explain the 'this' keyword in TypeScript.
The 'this' keyword in TypeScript is used to refer to the current instance of the object within a class or function.
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Ques 19. What is a module in TypeScript?
A module in TypeScript is a way to organize code into separate files, and it can include interfaces, classes, functions, and variables.
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Ques 20. What is the use of 'namespace' in TypeScript?
The 'namespace' keyword in TypeScript is used to group related code into a named scope, preventing naming conflicts with other parts of the program.
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Ques 21. Explain the 'async' and 'await' keywords in TypeScript.
'async' is used to declare an asynchronous function, and 'await' is used to pause the execution of the function until the promise is resolved.
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Ques 22. What are decorators in TypeScript?
Decorators are a special kind of declaration that can be attached to classes, methods, and properties to modify their behavior.
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Ques 23. What is the difference between 'interface' and 'type' in TypeScript?
'interface' is used for object shapes, while 'type' can be used for objects, unions, intersections, and primitives.
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Ques 24. Explain the concept of generics in TypeScript.
Generics in TypeScript allow you to write functions and classes that can work with any data type.
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Ques 25. How does TypeScript achieve type inference?
TypeScript uses a mechanism called type inference to automatically determine and assign types to variables based on their values and usage.
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Ques 26. What are type guards in TypeScript?
Type guards are expressions that help TypeScript narrow down the type of a variable within a certain code block.
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Ques 27. What is the 'keyof' operator in TypeScript?
The 'keyof' operator in TypeScript is used to obtain the union type of all possible keys of an object type.
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Ques 28. Explain the concept of declaration merging in TypeScript.
Declaration merging in TypeScript allows multiple declarations for the same entity to be combined into a single entity.
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Ques 29. How do you use the 'as' keyword for type assertions in TypeScript?
The 'as' keyword in TypeScript is used for type assertions, allowing you to tell the compiler that you know more about the type of a value than it does.
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Ques 30. Explain the concept of ambient declarations in TypeScript.
Ambient declarations in TypeScript are used to tell the compiler about the existence of external entities, such as libraries or globals, that are not defined in the current TypeScript file.
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Ques 31. How do you create an instance of an interface in TypeScript?
Interfaces in TypeScript are not directly instantiated. Instead, you can create an object literal that conforms to the shape of the interface.
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Ques 32. What is the 'this' type in TypeScript?
The 'this' type in TypeScript is used to represent the type of the instance of a class or object within a method.
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Ques 33. Explain the concept of abstract classes in TypeScript.
Abstract classes in TypeScript are classes that cannot be instantiated on their own and are meant to be subclassed. They may contain abstract methods that must be implemented by subclasses.
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Ques 34. What is the purpose of the 'namespace' keyword in TypeScript?
The 'namespace' keyword in TypeScript is used to group related code into a named scope, preventing naming conflicts with other parts of the program.
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Ques 35. How do you use the 'readonly' modifier with arrays and objects?
The 'readonly' modifier in TypeScript can be applied to arrays and objects using 'ReadonlyArray
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Experienced / Expert level questions & answers
Ques 36. What is the purpose of the 'never' type in TypeScript?
The 'never' type in TypeScript represents values that never occur, such as functions that always throw exceptions or never return.
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Ques 37. What is the 'this' parameter in TypeScript?
The 'this' parameter in TypeScript is a special parameter that allows you to explicitly specify the type of 'this' within a function.
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Ques 38. What is the 'never' type and where is it commonly used?
The 'never' type in TypeScript is used to represent values that never occur. It is commonly used in functions that always throw exceptions or never return.
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