Type Annotations & Inference - Concepts
Explore the key concepts of type annotations & inference with practical examples and exercises.
45 min•By Priygop Team•Last updated: Feb 2026
Introduction to Type Annotations & Inference
In this section, we cover the fundamental aspects of type annotations & inference. You'll learn core concepts, see real-world examples, and understand how to apply them in your projects.
Key Concepts
- Understanding the core principles of type annotations & inference
- Practical applications and real-world use cases
- Step-by-step implementation guides
- Common patterns and best practices
- Tips for debugging and troubleshooting
- Performance optimization techniques
Type Annotations & Inference - Code Example
Example
// Type Annotations
let username: string = "Alice";
let age: number = 25;
let isActive: boolean = true;
let scores: number[] = [95, 87, 92];
let person: [string, number] = ["Bob", 30]; // Tuple
// Type Inference
let city = "NYC"; // TypeScript infers string
let count = 42; // TypeScript infers number
// Union Types
let id: string | number = "abc123";
id = 456; // Also valid
// Literal Types
let direction: "up" | "down" | "left" | "right" = "up";Try It Yourself: Type Annotations & Inference
Try It Yourself: Type Annotations & InferenceJavaScript⚠ 1 error
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Line 1: JS Error: Unexpected token ':'
💡 Missing or extra {}()[] or operator near the error.
JavaScript Editor
✕ 1 errorTab = 2 spaces
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