TypeScript Beginner Tutorial 5 | Basic Variable Types 1

Introduction

This tutorial is designed for beginners looking to understand the basic variable types in TypeScript. By the end of this guide, you'll be familiar with the fundamental variable types—number, string, boolean, null, undefined, and arrays—and how to declare them in your TypeScript code.

Step 1: Understanding Number Variables

TypeScript allows you to define variables with specific types. The number type is used for both integer and floating-point numbers.

• To declare a number variable, use the let keyword followed by the variable name and type.

let x: number = 10;

Practical Tip: Always initialize your number variables to avoid unexpected results later in your code.

Step 2: Working with String Variables

String variables are used to store text.

• Declare a string variable using the let keyword, specifying the string type.

let name: string = 'TypeScript';

Common Pitfall: Ensure to enclose string values in either single quotes (' ') or double quotes (" ").

Step 3: Using Boolean Variables

Boolean variables represent true or false values, which are essential for control flow in programming.

• To declare a boolean variable, use the let keyword and specify the boolean type.

let learningTypeScript: boolean = true;

Real-World Application: Use boolean variables for conditional statements to control the flow of your program.

Step 4: Understanding Undefined Variables

An undefined variable is one that has been declared but not assigned a value.

• Declare an undefined variable as follows:

let u: undefined = undefined;

Practical Tip: Use undefined to signal that a variable exists but hasn’t been initialized yet.

Step 5: Working with Null Variables

The null type represents the intentional absence of any object value.

• To declare a null variable, use:

let n: null = null;

Important Note: null is often used to indicate that a variable intentionally has no value.

Step 6: Understanding Subtypes of Null and Undefined

Both null and undefined can be assigned to other types like boolean, number, and string.

• For instance, you can assign null to a number variable:

let num: number | null = null;

Tip: This flexibility allows you to create more dynamic and robust applications.

Conclusion

In this tutorial, you learned about the basic variable types in TypeScript, including number, string, boolean, null, and undefined. Understanding these types is crucial for writing effective TypeScript code.

Next Steps

• Experiment with declaring various variable types in your own TypeScript projects.
• Explore more advanced concepts, such as type inference and union types, to further enhance your programming skills.