TypeScript Beginner Tutorial 4 | Variables

Introduction

This tutorial is designed for beginners who want to learn about variables in TypeScript. Understanding how to properly declare and use variables is fundamental to programming. In this guide, we will cover variable declarations, type inference, and how these concepts can enhance your coding experience.

Step 1: Declare a Variable with Value

To declare a variable and assign a value, you can use the let keyword. Here’s how you can do it:

• Open your TypeScript file (with a .ts extension).
• Add the following code:

let a = 10;
a = "Raghav"; // This will cause an error because 'a' is inferred as a number

Practical Tip: TypeScript is a statically typed language, which means that it will infer the type of the variable based on the initial assignment. In the example above, a is initially set to a number.

Step 2: Declare a Variable Without Initial Value

You can also declare a variable without assigning a value immediately. This is useful when you plan to assign a value later in your code.

• Add the following line to your TypeScript file:

let x; // 'x' is declared but not initialized

Common Pitfall: Remember that a variable declared without an initial value is undefined until you assign it. Be cautious when using it before initialization.

Step 3: Understand Type Inference

TypeScript uses type inference to determine the type of a variable based on its assigned value. This feature helps with code completion and IntelliSense in your IDE.

• For example, you can declare a variable like this:

let x = 10; // TypeScript infers that 'x' is of type number

• If you later try to assign a different type, such as a string, TypeScript will throw an error:

x = "Hello"; // Error: Type 'string' is not assignable to type 'number'

Practical Tip: Leveraging type inference can significantly improve your coding efficiency by reducing the amount of type annotations you need to write.

Conclusion

In this tutorial, we covered how to declare variables in TypeScript, the concept of type inference, and the benefits of using these features in your coding practices.

Key Takeaways

• Use let to declare variables.
• You can declare variables without assigning values.
• Type inference enhances code readability and helps with autocompletion.

Next Steps

To further your understanding of TypeScript, consider exploring topics such as variable scopes, type annotations, and advanced types. Practice writing code snippets and experimenting with different variable types to solidify your knowledge. Happy coding!