Top 50 FAQs for TypeScript

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What is TypeScript?

TypeScript is a superset of JavaScript that adds static typing to the language, enhancing developer tooling and providing better support for large-scale applications.

Why use TypeScript over JavaScript?

TypeScript offers static typing, improved tooling, and additional language features that make code more maintainable and catch errors early in the development process.

How do I install TypeScript?

You can install TypeScript using npm (Node Package Manager) with the command: npm install -g typescript.

How does TypeScript differ from JavaScript?

TypeScript includes static typing, interfaces, and other features not present in JavaScript. It compiles to JavaScript, allowing for seamless integration with existing JavaScript code.

What are the benefits of static typing in TypeScript?

Static typing helps catch errors during development, provides better code documentation, and improves code editor support with features like autocompletion and type checking.

How do I create a TypeScript file?

Create a file with a .ts extension, such as example.ts, and start writing TypeScript code.

How does TypeScript handle data types?

TypeScript supports various data types, including number, string, boolean, array, tuple, enum, any, void, null, and undefined.

Can TypeScript code be directly run in browsers?

No, TypeScript code needs to be transpiled to JavaScript before running in browsers. The TypeScript compiler (tsc) handles this process.

What is transpilation in TypeScript?

Transpilation is the process of converting TypeScript code to equivalent JavaScript code. TypeScript files are transpiled using the tsc compiler.

How do I compile TypeScript code?

Use the tsc command followed by the name of the TypeScript file, like tsc example.ts. This generates a corresponding JavaScript file.

What is a TypeScript interface?

An interface in TypeScript defines a contract for the shape of an object, specifying properties and their types.

How do I use interfaces in TypeScript?

Declare an interface using the interface keyword, and then use it to define the structure of objects or classes.

What are TypeScript generics?

Generics allow you to create flexible and reusable components by allowing types to be parameterized.

How does TypeScript handle classes?

TypeScript supports class-based object-oriented programming with features like constructors, inheritance, and access modifiers.

What is the role of TypeScript decorators?

Decorators are a way to add metadata to classes, methods, or properties in TypeScript. They are widely used in frameworks like Angular.

How do I use TypeScript with Node.js?

TypeScript can be used with Node.js by installing the ts-node package and using it to run TypeScript files directly.

Can TypeScript be used for frontend development?

Yes, TypeScript is commonly used for frontend development, especially in projects built with frameworks like Angular and React.

How does TypeScript support async/await?

TypeScript natively supports asynchronous programming with async/await syntax, making it easier to work with asynchronous operations.

What is the role of the tsconfig.json file in TypeScript?

The tsconfig.json file contains configuration settings for the TypeScript compiler. It defines compiler options, file inclusion/exclusion rules, and more.

How do I set up a basic tsconfig.json file?

Run tsc –init to generate a basic tsconfig.json file. Adjust its settings according to your project’s needs.

What is the TypeScript compiler watch mode?

The watch mode (tsc -w) allows the TypeScript compiler to watch for changes in files and automatically recompile when modifications are detected.

How do I handle nullable types in TypeScript?

TypeScript has strict null checks, and you can use the null and undefined types or the –strictNullChecks compiler option to handle nullable types.

What is the never type in TypeScript?

The never type represents values that will never occur. It is often used for functions that throw exceptions or enter infinite loops.

How do I use TypeScript with React?

TypeScript can be used with React by installing the typescript and @types/react packages, and configuring the tsconfig.json file.

What is the readonly modifier in TypeScript?

The readonly modifier is used to create properties that can only be assigned a value during object initialization.

How does TypeScript handle union types?

Union types allow a variable to have multiple types. They are denoted using the | operator.

What is the purpose of the keyof keyword in TypeScript?

The keyof keyword is used to obtain the union type of all possible property names of a given type.

How do I use TypeScript with Express.js?

TypeScript can be used with Express.js by installing the typescript and @types/express packages, and configuring the tsconfig.json file.

What are ambient declarations in TypeScript?

Ambient declarations allow you to define types for variables that are declared elsewhere, such as in third-party libraries.

How does TypeScript handle type assertions?

Type assertions allow you to tell the compiler that you know the type of a variable better than it does. They are done using the or value as Type syntax.

What is the –strict flag in TypeScript?

The –strict flag is a compiler option that enables strict type checking and additional TypeScript strictness options.

How do I use TypeScript with Vue.js?

TypeScript can be used with Vue.js by installing the typescript and @types/vue packages, and configuring the tsconfig.json file.

What is the role of declaration files (d.ts) in TypeScript?

Declaration files provide type information for JavaScript code and enable TypeScript to understand the types used in non-TypeScript code.

How does TypeScript handle enums?

TypeScript supports enums, allowing developers to define named constant values.

What is the as const syntax in TypeScript?

The as const syntax is used to assert a variable as a literal type, making TypeScript treat it as an immutable constant.

How does TypeScript handle conditional types?

Conditional types in TypeScript allow you to create types that depend on other types.

What is the TypeScript namespace keyword used for?

The namespace keyword in TypeScript is used to organize code into named spaces, preventing naming conflicts.

How do I use TypeScript with Jest for testing?

TypeScript can be used with Jest by installing the typescript, ts-jest, and @types/jest packages, and configuring the Jest and TypeScript settings.

What is the –isolatedModules flag in TypeScript?

The –isolatedModules flag enforces that each file is a separate module, preventing unintended sharing of variables across files.

How do I use TypeScript with Webpack?

TypeScript can be integrated with Webpack by installing the typescript and ts-loader packages, and configuring the Webpack settings.

What is the purpose of the NonNullable type in TypeScript?

The NonNullable type excludes null and undefined from a given type, ensuring that variables of that type are not nullable.

How do I use decorators in TypeScript?

Decorators are used by prefixing them with an @ symbol above declarations like classes or methods. They can modify or annotate the behavior of the associated code.

What is the unknown type in TypeScript?

The unknown type represents a value about which the TypeScript compiler knows nothing. It is often used when the type of a value is dynamically determined.

How do I use TypeScript with GraphQL?

TypeScript can be used with GraphQL by installing the necessary packages and creating type definitions for GraphQL schemas.

What is the in operator used for in TypeScript?

The in operator is used to check if a property exists in an object. It is often used in conditional types.

How does TypeScript handle optional chaining?

Optional chaining (?.) allows developers to access properties or methods on an object without causing an error if the object is null or undefined.

What is the TypeScript mapped types feature?

Mapped types allow you to create new types based on existing ones, often used for creating variations of object properties.

How do I configure ESLint for TypeScript?

ESLint can be configured for TypeScript by installing the necessary packages (@typescript-eslint/eslint-plugin, @typescript-eslint/parser) and creating a configuration file.

What is the –strictFunctionTypes flag in TypeScript?

The –strictFunctionTypes flag enforces strict checking of function parameter types in function types.

How do I contribute to the TypeScript open-source project?

Contributions to the TypeScript project can be made by forking the repository on GitHub, making changes, and creating a pull request.

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