Hello, Space Explorer! Today, we're going to delve into the TypeScript data types. Think of data types as different celestial objects in our universe, each with its unique properties and uses. We'll explore five core TypeScript types — Number, String, Boolean, Void, and Undefined.

In TypeScript, types are categorized based on their characteristics. Understanding this is akin to realizing that Earth is a planet, not a star or an asteroid. This knowledge helps us predict behaviors in different situations.

First, we're going to uncover numerical values through the Number type, which stores numbers such as 10 (integer numbers) or -2.19 (floating point numbers, i.e., numbers with a decimal point). Let's visualize it:

TypeScript
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1let numPlanets: number = 8; // Declaring an integer number variable
2console.log(numPlanets); // Prints: 8
3
4let planetWeight: number = 3.52; // Declaring a floating point number variable with a decimal point
5console.log(planetWeight); // Prints: 3.52

Upon running this code, you'll see 8 and 3.52 printed — these are the values of our declared numPlanets and planetWeight variables.

Next, we'll traverse the textual space with the String type, which represents any text data. Let's create planetName and assign it the value "Earth".

TypeScript
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1let planetName: string = "Earth"; // Declaring a string variable
2console.log(planetName); // Prints: "Earth"

Seeing "Earth" printed to the console illustrates how the String variable planetName works!

In the TypeScript universe, the Boolean type is like binary stars, manifesting as either true (correct, valid) or false (incorrect, invalid). These are often used in programming to make decisions. Let's see it in action:

TypeScript
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1let earthIsAPlanet: boolean = true; // Declaring a boolean variable
2console.log(earthIsAPlanet); // Prints: true
3
4let appleIsAPlanet: boolean = false; // Declaring another boolean variable
5console.log(appleIsAPlanet); // Prints: false

When you run this code, true and false are printed, which indicates that the earthIsAPlanet is true and appleIsAPlanet is false.

In TypeScript, void is used when there's no data. This type is usually used as the return type of functions that do not return anything. We'll learn more about functions soon.

TypeScript
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1function printHello(): void {
2  console.log('Hello');
3}

When this function is run, it prints Hello and does not return anything.

undefined, a designation for a variable that is declared but not assigned a value, is akin to spotting a planet about which we know nothing.

TypeScript
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1let newPlanet: undefined; // Declaring a variable without assigning a value
2console.log(newPlanet); // Prints: undefined

When you run this code, undefined is printed, indicating that newPlanet has been declared but not assigned a value.

Great job! We've journeyed through TypeScript types: Number, String, Boolean, Void, and Undefined. Now, let's progress toward practice exercises to reinforce this knowledge. As you learn more with each exercise, you'll gain a more profound understanding of TypeScript types. Remember, practice is key! Let's continue exploring!