Lære Why Use TypeScript? | Introduction to TypeScript

As you start working with JavaScript on larger projects, you might notice some recurring issues. JavaScript's flexibility comes from its dynamic typing, but this can lead to unexpected bugs that are hard to track down. For example, a variable can hold any type of value, so you might accidentally use a string where a number is expected, or vice versa. These mistakes may only show up at runtime, making them difficult and costly to fix. This lack of type safety can also make it harder to maintain and refactor code, especially as your codebase grows or when multiple developers are involved.

TypeScript was created to solve these problems by adding static typing to JavaScript. With TypeScript, you can specify what types of values your variables, function parameters, and return values should have. This allows errors to be caught during development, before your code runs, making your applications more robust and maintainable.


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// JavaScript example with a hidden bug
function multiply(a, b) {
  return a * b;
}

const result = multiply("5", 2); // JavaScript tries to convert "5" to a number, but what if you pass "five"?
console.log(result); // 10, but multiply("five", 2) would return NaN


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// TypeScript version prevents the bug
function multiply(a: number, b: number): number {
  return a * b;
}

// const result = multiply("5", 2); // Error: Argument of type 'string' is not assignable to parameter of type 'number'
const result = multiply(5, 2); // Correct usage
console.log(result); // 10

In real-world development, TypeScript offers several key advantages that improve both code quality and the developer experience. For large teams, TypeScript's static typing makes it easier to understand how different parts of the code interact, reducing the risk of introducing bugs during updates or refactoring. When onboarding new team members, clear type definitions serve as built-in documentation, helping everyone quickly grasp how to use functions and objects correctly. Many popular frameworks and libraries now provide TypeScript type definitions, allowing you to catch mistakes as you code and benefit from enhanced editor features like autocomplete and inline documentation. Ultimately, TypeScript leads to more reliable, maintainable, and scalable codebases, especially as your projects grow in size and complexity.

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              1234567
            
// JavaScript example with a hidden bug
function multiply(a, b) {
  return a * b;
}

const result = multiply("5", 2); // JavaScript tries to convert "5" to a number, but what if you pass "five"?
console.log(result); // 10, but multiply("five", 2) would return NaN


              12345678
            
// TypeScript version prevents the bug
function multiply(a: number, b: number): number {
  return a * b;
}

// const result = multiply("5", 2); // Error: Argument of type 'string' is not assignable to parameter of type 'number'
const result = multiply(5, 2); // Correct usage
console.log(result); // 10

Alt var klart?

Takk for tilbakemeldingene dine!

Seksjon 1. Kapittel 2