Interview Questions and Answers

TypeScript is a superset of JavaScript that adds static typing and other features to the language.

'let' is used to declare variables with block scope, while 'const' is used to declare constants with block scope that cannot be reassigned.

The basic data types in TypeScript are number, string, boolean, null, undefined, and object.

Interfaces in TypeScript are defined using the 'interface' keyword, followed by the interface name and a set of property declarations.

The 'any' type in TypeScript is used to represent a dynamic type that can hold values of any type, and it bypasses type checking.

Arrays in TypeScript can be declared using the syntax 'let myArray: number[] = [1, 2, 3];' or 'let myArray: Array = [1, 2, 3];'.

Errors in TypeScript can be handled using try-catch blocks, similar to JavaScript.

Optional parameters in TypeScript are denoted by adding a '?' after the parameter name in the function declaration.

The 'readonly' modifier in TypeScript is used to make properties of an object immutable after their initial assignment.

Union types in TypeScript allow a variable to hold values of multiple types, separated by the '|' symbol.

Classes in TypeScript are declared using the 'class' keyword, and objects are created using the 'new' keyword.

The 'for...of' loop in TypeScript is used to iterate over the values of an iterable object, such as an array or a string.

The 'import' statement in TypeScript is used to import modules or exports from other files.

The 'in' operator in TypeScript is used to check if a property exists in an object.

A tuple in TypeScript is a fixed-size, ordered list of elements where each element can have a different type.

The 'export' keyword in TypeScript is used to make functions, variables, or classes available for use in other files by importing them.

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.

The 'this' keyword in TypeScript is used to refer to the current instance of the object within a class or function.

A module in TypeScript is a way to organize code into separate files, and it can include interfaces, classes, functions, and variables.

The 'namespace' keyword in TypeScript is used to group related code into a named scope, preventing naming conflicts with other parts of the program.

'async' is used to declare an asynchronous function, and 'await' is used to pause the execution of the function until the promise is resolved.

Decorators are a special kind of declaration that can be attached to classes, methods, and properties to modify their behavior.

'interface' is used for object shapes, while 'type' can be used for objects, unions, intersections, and primitives.

Generics in TypeScript allow you to write functions and classes that can work with any data type.

TypeScript uses a mechanism called type inference to automatically determine and assign types to variables based on their values and usage.

Type guards are expressions that help TypeScript narrow down the type of a variable within a certain code block.

The 'keyof' operator in TypeScript is used to obtain the union type of all possible keys of an object type.

Declaration merging in TypeScript allows multiple declarations for the same entity to be combined into a single entity.

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.

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.

Interfaces in TypeScript are not directly instantiated. Instead, you can create an object literal that conforms to the shape of the interface.

The 'this' type in TypeScript is used to represent the type of the instance of a class or object within a method.

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.

The 'namespace' keyword in TypeScript is used to group related code into a named scope, preventing naming conflicts with other parts of the program.

The 'readonly' modifier in TypeScript can be applied to arrays and objects using 'ReadonlyArray' and 'Readonly' types to make them immutable.

The 'never' type in TypeScript represents values that never occur, such as functions that always throw exceptions or never return.

The 'this' parameter in TypeScript is a special parameter that allows you to explicitly specify the type of 'this' within a function.

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.