TypeScript Programming Language 2025
TypeScript is a JavaScript-based, strongly typed programming language that provides improved tooling at any size. Microsoft Corporation created and maintained this object-oriented programming language. It’s a superset of JavaScript that includes all of its features. TypeScript compiles to standard-compliant JavaScript. It is a rigorous syntactical superset of JavaScript with the addition of optional static typing. It’s built for the creation of huge apps and converts to JavaScript. Existing JavaScript programs are likewise valid TypeScript programs because it is a superset of JavaScript.
TypeScript can be used to create both client-side and server-side JavaScript applications. It supports definition files, which define the structure of existing JavaScript libraries in the same way as C++ header files describe the structure of existing object files. Other applications can use the values defined in the files as if they were TypeScript entities with statically typed values. The TypeScript compiler is written in TypeScript and then compiled into JavaScript. The Apache License 2.0 governs its use.
Free TypeScript Practice Test Online
To promote a stronger interaction with your editor, TypeScript adds additional syntax to JavaScript. JavaScript is the beginning and the end of TypeScript. The essential building parts of your application are taken from JavaScript by Typescript. After two years of internal development at Microsoft, TypeScript was first made public in October 2012 (at version 0.8). It arose from Microsoft’s and their external customers’ frustrations with JavaScript’s limitations in creating large-scale applications. Due to the difficulty of working with complicated JavaScript code, custom tools were requested to make developing components in the language easier.
Uri.EscapeDataString for TypeScript
Except for RFC 2396 unreserved characters, the EscapeDataString function converts all characters to their hexadecimal equivalent. The EscapeDataString function converts all characters, save RFC 3986 unreserved characters, to their hexadecimal equivalent if International Resource Identifiers (IRIs) or Internationalized Domain Name (IDN) parsing is enabled. Before being escaped, all Unicode characters are translated to UTF-8 format. This method assumes stringToEscape does not contain any escape sequences. The string is escaped by default according to RFC 2396. The string is escaped according to RFC 3986 and RFC 3987 if International Resource Identifiers (IRIs) or Internationalized Domain Name (IDN) processing is enabled.
String cannot be used as an index type TypeScript
“Type ‘String’ cannot be used as an index type” is a warning. When we use the String type instead of a string, we get a TypeScript error (lowercase s). To fix the problem, make sure your TypeScript code uses the string type with lowercase s. The error occurred because the primitive number, string, and boolean types differ from the non-primitive Number, String, Boolean, Object, etc. Non-primitive types are objects that should never be used in TypeScript for typing values.
TypeScript Exclamation Mark
The Non-Null Assertion Operator is the “Exclamation Mark” operator, and it tells the compiler to ignore undefined or null types. It’s handy for searching for items in a list and dealing with Refs in react. If a null value is assigned to a typed variable, TypeScript will complain. The exclamation, bang, or! operator is used here to force the compiler to interpret the value as non-null. When utilizing it, developers must be exceedingly cautious, as misuse can result in a runtime error, which TypeScript could prevent. However, it shortens your code and eliminates the need for some additional checks.
Ignore TypeScript Error
Typescript is a superset of Javascript that is strongly typed. It can be inconvenient at times. Finding type definitions for external libraries appears to be your major headache. The solution to this problem is to disable type checking.
- Add the following remark before the line to disable the compiler error for that line:
- // @ts-ignore
- If you’re experiencing a lint error, try the following:
- error Do not use “@ts-ignore” because it alters compilation errors @typescript-eslint/ban-ts-comment
- TL;DR: to ignore a line:
- // eslint-disable-next-line @typescript-eslint/ban-ts-comment
- // @ts-ignore
- Add the following comment at the start of the file to disable type checking for the entire file:
- // @ts-nocheck
Module has no Exported Member TypeScript
When we try to import a member that doesn’t exist in the provided module, we get the error “Module has no exported member.” Double-check that the module exports the correct member and that you haven’t mistyped or named for default import to fix the problem.
TypeScript Abstract Class
Abstract classes are mostly used for inheritance, with other classes being able to derive from them. An instance of an abstract class cannot be created. One or more abstract methods or property declarations are usually included in an abstract class. All abstract methods must be defined in the class that extends the abstract class. Abstract classes serve as a foundation for the creation of further classes. They can’t be used straight away. An abstract class, unlike an interface, may contain implementation details for its members. Abstract classes and abstract methods within an abstract class are defined using the abstract keyword. The abstract keyword is used to declare an abstract class:
abstract class Employee {
    //…
}
TypeScript Double Question Mark
In Angular and Typescript, the double question marks(??) or nullish coalescing operator is used to set default values to null or undefined variables. It’s included in the Typescript 3.7 release. You will find it in your everyday programs if you are familiar with the C# programming language. The nullish coalescing operator was not always supported by TypeScript. TypeScript generates JavaScript from code. This operator, however, was not always available in JavaScript. JavaScript is constantly evolving, and a set of ECMA standards defines it. The nullish coalescing operator has a fairly simple syntax: following the variable, use double question marks ‘??’, followed by the default value.
var dValue = nValue ?? “defaultValue”;
TypeScript Extend Type
In TypeScript, there are a few different ways to extend object-like types with interfaces, including type aliases. Even official documents state that they are essentially interchangeable in those instances; thus, it comes down to personal preference, organization, habit, and so on. Use TypeScript interfaces instead if you want to define distinct attributes on the same type in different places of your program. The extends keyword in TypeScript can be used to extend types. Only interfaces and classes can use the keyword extends.
TypeScript Operators
A symbol that operates on a value or data is known as an operator. It specifies which function will be applied to the data. Operands are the data that operators operate with. It can be used with one or more values to produce a single value. The TypeScript program includes all of the usual JavaScript operators. Unary operators are those that only require one operand. Binary operators are those that take two operands. There is one ternary operator in Typescript that takes three operands. The following are the major TypeScript operators:
- Arithmetic operators
- Logical operators
- Relational operators
- Bitwise operators
- Assignment operators
- Ternary/conditional operator
- String operator
- Type Operator
Abstract Factory Design Pattern TypeScript
Abstract Factory is a design pattern for constructing complete product families without identifying their concrete classes. It defines an interface for constructing all different products, while concrete factory classes handle the actual product development. Each factory type is associated with a specific product category. This pattern solves the problem of building multiple sorts of objects dependent on a client’s interaction with the system, and it is unknown which object the client will produce ahead of time. Furthermore, these objects are linked via object families, distinguishing them by context or object type while working with different factories. The Abstract Factory pattern provides a number of benefits, which can be stated as follows:
- Cleaner code because the Single Obligation Principle (SRP) is followed, and the responsibility for creating the concrete product is passed to the concrete creation class rather than the client class.
- It is ensured that products made by the same manufacturer class are compatible.
- Cleaner code because the Single Obligation Principle (SRP) is followed, as the responsibility for creating the concrete product is passed to the concrete creator class rather than the client class.
- The Open-Closed Principle ensures clean code because new product families can be introduced without affecting the current code.
Distinct TypeScript
Although the JavaScript Array object lacks a method, the filter can be used to achieve the same result. Using native array methods in JavaScript is one technique to extract distinct values from an array of objects. You can use a Set to remove non-unique values from an array in TypeScript, which is a neat trick. When you combine this with Array.from, you have a one-liner for removing non-unique data.
const unqiueValues = Array.from(new Set(YOUR_ARRAY_HERE))
Typescript code example: filtering an array for distinct values:
- {“id”:1,”name”:”red”}
- {“id”:2,”name”:”yellow”}
- {“id”:3,”name”:”green”}
- {“id”:4,”name”:”blue”}
- {“id”:5,”name”:”orange”}
Learning TypeScript PDF
Learning TypeScript will give you a new perspective on JavaScript and a better comprehension of it. You’ve come to the correct place if you’re interested in learning TypeScript and are seeking quality resources such as books, classes, and tutorials. You might want to look into typescript tutorial PDF, effective typescript PDF, mastering typescript PDF, and typescript book PDF, all available online. We also propose that you take online tests to assess your understanding, such as the typescript test and typescript certification exam. Learning the fundamentals of TypeScript takes roughly a month if you study for at least one hour per day. Expect to spend at least six months learning TypeScript before you’re ready to use it in a professional development setting.
Typescript Questions and Answers
It is best to create a compiler configuration before beginning a TypeScript project. This can be accomplished with tsc —init, which will put up a basic project using documented compiler parameters.
To import a JSON file into TypeScript, follow these steps:
- In your tsconfig.json file, set resolveJsonModule to true.
- In tsconfig.json, set esModuleInterop to true.
- Import employee from ‘./employee.json’ as a JSON file.
Microsoft created and maintained the TypeScript programming language. It is a rigorous syntactical superset of JavaScript with the addition of optional static typing. It’s intended for the creation of huge apps and converts to JavaScript.
Refactoring code in the IDE is significantly easier in Typescript, and it works far better than vanilla Javascript. A “wrongly” named variable in JS can sometimes cause your refactoring to fail. It’s easier for the code editor to discover specific, associated variables, functions, classes, and so on with Typescript.
Babel will be required if you require custom transformations.
Type inference is the mechanism through which TypeScript infers types from JavaScript code. Use type inference for greater code maintainability, but add annotations when TypeScript becomes confused.
For JavaScript IDEs and practices like static checking, TypeScript provides highly productive development tools. TypeScript simplifies the reading and understanding of code. We can make a significant improvement over simple JavaScript with TypeScript. TypeScript provides all of the advantages of ES6 (ECMAScript 6) while also increasing productivity.
Type tsc -v in your terminal or command prompt to see if TypeScript is installed correctly. The TypeScript version should now appear on the screen.
You can install TypeScript globally with npm, which means you can run the tsc command from wherever in your terminal.
TypeScript is becoming increasingly popular, and it’s worth studying whether you’ve worked with other programming languages before or are new to the field.
You’ll need to install the TypeScript compiler to run TypeScript files. Run tsc -v to see if it was installed successfully. It will show you the TypeScript version installed on your computer.
- TypeScript will generate a js file with the same name as tsc filename.ts at runtime. Launch node filename.js to run the created js file.
- With some content, a TypeScript file named helloworld.ts is created. To run helloworld.ts, simply type the following commands. tsc
      helloworld.ts
      node helloworld.js
TypeScript cannot be learned without first learning JavaScript.
In TypeScript, interfaces are constructed by using the interface keyword, followed by the interface’s name, and then a {} block with the interface’s content.
TypeScript is a little more difficult to understand than JavaScript.
Because TypeScript is so important to the framework, learning it before using it is highly encouraged.
An interface is an abstract type in TypeScript that tells the compiler what property names an object can have. When you define an object with properties, TypeScript provides implicit interfaces. It begins by using TypeScript’s type inference capabilities to look at the object’s property name and data type.
Microsoft Corporation created TypeScript, an object-oriented programming language, while JavaScript is a web programming language. TypeScript is an open-source programming language for creating large-scale web apps, whereas JavaScript is a server-side programming language for creating interactive web pages.
TypeScript constantly highlights compilation mistakes during development (pre-compilation). Because JavaScript is an interpreted language, it is less likely to encounter runtime problems. Static/strong typing is supported in TypeScript.
It will take you anywhere from three months to a year to master because you’ll also need to master JavaScript and type systems! If you know JavaScript and how type systems work, you’ll be able to pick up the basics of TypeScript in a day or two.
- Include the tsconfig.json file in the project.
- Connect to a build tool.
- All. js files should be replaced with. ts files.
- Check for any errors.
There are many ways to convert a string to a number in typescript. To convert a string to a number, we can use the ‘+’ unary operator, Number(), parseInt(), or parseFloat() functions.
The forEach() method is an array method that runs a function on each element of an array. It works with JavaScript data types like Arrays, Maps, Sets, etc. It is a good way to display an array of elements.
To address this, TypeScript provides the concept of arrays. An array is a collection of values that are all the same. An array is a collection of values of the same data type, to put it simply. It’s a type that you create yourself.
TypeScript differs from JavaScript in that the former is a scripting language, while the latter is an object-oriented language. Module support is made easier in TypeScript but not in JavaScript. JavaScript does not have an interface. However, TypeScript does.
TypeScript is a “typed superset of JavaScript that compiles to plain JavaScript,” while React is a “JavaScript library for designing user interfaces.” We effectively build our UIs using a typed version of JavaScript by combining them.
The realm of frontend applications is a natural fit for TypeScript.
OOP is a programming paradigm, while TypeScript is a programming language. TypeScript does a good job of expressing OOP (as JavaScript). If a language supports many programming paradigms, it is said to be a “multi-paradigm” (be it OOP, FP, Imperative, etc.). All of these are supported by TypeScript and JavaScript.
According to Stack Overflow’s 2025 Developer Survey, TypeScript is almost as popular as PYPL suggests, ranking sixth among 83,000 developers. One of the most reputable and eagerly anticipated developer surveys is the Stack Overflow annual survey.
TypeScript delivers superior IntelliSense and code completion for JSX when used with React.
Visual Studio Code, which comes with excellent TypeScript support, is highly recommended for developing Vue apps using TypeScript. Get the excellent Vetur addon if you use single-file components (SFCs), allowing TypeScript inference inside SFCs and many other great features.
Depending on your preference, you can learn TypeScript programming through video or book lessons and courses.