JavaScript Basics: Values, Types, and Operators

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🔢 Numbers

Numbers represent all kinds of numeric data in JavaScript.

let age = 25;
let pi = 3.14;
let speedOfLight = 2.998e8; // 2.998 × 10^8

JavaScript uses 64 bits to store each number — enough to represent most values, but not all decimals are exact.

Arithmetic Operators

console.log(100 + 4 * 11); // 144
console.log((100 + 4) * 11); // 1144
console.log(10 % 3); // 1 (remainder)

Common operators:

• + addition
• - subtraction
• * multiplication
• / division
• % remainder (modulo)

Special Numbers

console.log(Infinity - 1); // Infinity
console.log(0 / 0); // NaN (Not a Number)

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🧵 Strings

Strings represent text and are wrapped in quotes.

let message = "Hello, world!";
let lineBreak = "First line\nSecond line";

You can combine strings using +:

console.log("con" + "cat" + "enate"); // concatenate

Template literals (backticks) allow embedding values:

let x = 100;
console.log(`Half of ${x} is ${x / 2}`);
// → Half of 100 is 50

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⚖️ Booleans

Booleans are simple true/false values used for logic and conditions.

console.log(3 > 2); // true
console.log(3 < 2); // false

Comparison Operators

Operator	Meaning
>	greater than
<	less than
>=	greater or equal
<=	less or equal
==	equal (with type conversion)
===	equal (strict, no conversion)
!=	not equal
!==	not equal (strict)

Example:

console.log("Garnet" != "Ruby"); // true
console.log(NaN == NaN); // false

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🔣 Logical Operators

Logical operators let you combine Boolean values:

console.log(true && false); // false
console.log(true || false); // true
console.log(!true); // false

• && → AND (both must be true)
• || → OR (at least one true)
• ! → NOT (flips the value)

Short-Circuiting

console.log(null || "user"); // "user"
console.log("Agnes" || "user"); // "Agnes"

• || returns the first truthy value.
• && returns the first falsy value.
• ?? (nullish coalescing) only checks for null or undefined.

console.log(0 || 100);  // 100
console.log(0 ?? 100);  // 0
console.log(null ?? 100); // 100

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🧩 Other Useful Operators

typeof

Tells you the type of a value.

console.log(typeof 4.5);  // "number"
console.log(typeof "hi"); // "string"

Ternary Operator (?:)

A compact way to write conditions.

let age = 20;
console.log(age > 18 ? "Adult" : "Minor"); // "Adult"

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🚫 Empty Values

null and undefined represent the absence of a value.

let x;
console.log(x); // undefined
x = null;
console.log(x); // null

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🔄 Type Conversion

JavaScript often converts types automatically — sometimes in confusing ways!

console.log(8 * null);     // 0
console.log("5" - 1);      // 4
console.log("5" + 1);      // "51"
console.log("five" * 2);   // NaN
console.log(false == 0);   // true

Use === to avoid unwanted conversions.

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🧠 Summary

• Numbers, Strings, Booleans, null, and undefined are the basic value types.
• Operators (+, -, *, /, %, ==, &&, ||, etc.) let you combine and transform values.
• Use === and !== to avoid confusing type conversions.
• Strings use backticks (`) for embedded expressions.
• Logical operators like || and ?? can set default values.

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🪄 With these basics, you can already use JavaScript like a calculator that speaks logic — and you’re ready for the next step: building real programs!