JavaScript Math and Numbers

What are Numbers in JavaScript?

JavaScript uses a single Number type to represent all kinds of numeric values — including:

Integers: 1, 42, -5
Floating-point numbers (decimals): 3.14, -0.99
Exponential numbers: 1.5e3 (equals 1500)

let a = 10;
let b = 3.14;

NOTE:JavaScript does not have different types for int and float like some other languages.

Basic Arithmetic Operators

Operator	Description	Example
`+`	Addition	`5 + 3` → `8`
`-`	Subtraction	`5 - 2` → `3`
`*`	Multiplication	`5 * 3` → `15`
`/`	Division	`15 / 3` → `5`
`%`	Modulus (remainder)	`7 / 3` → `1`
`**`	Exponentiation	`2**3` → `8`

Increment and Decrement

let x = 5;
x++;  // x = 6
x--;  // x = 5

You can also use:

x += 2
x *= 3
x /= 2, etc.

Working with the `Math` Object

JavaScript provides a built-in Math object with many methods and properties.

Common Math Methods

Method	Description	Example
`Math.round()`	Rounds to nearest integer	`Math.round(4.6)` → `5`
`Math.floor()`	Rounds down	`Math.floor(4.9)` → `4`
`Math.ceil()`	Rounds up	`Math.ceil(4.1)` → `5`
`Math.trunc()`	Removes decimal part	`Math.trunc(4.8)` → `4`
`Math.abs()`	Absolute value	`Math.abs(-10)` → `10`
`Math.pow()`	Exponentiation	`Math.pow(2, 3)` → `8`
`Math.sqrt()`	Square root	`Math.sqrt(16)` → `4`
`Math.max()`	Highest value	`Math.max(1, 5, 3)` → `5`
`Math.min()`	Lowest value	`Math.min(1, 5, 3)` → `1`
`Math.random()`	Random number between 0 and 1	`Math.random()`

Random Number Between a Range

// Random number between 1 and 10
let random = Math.floor(Math.random() * 10) + 1;
console.log(random);

Number Conversion

`parseInt()` - Converts string to integer

let n = parseInt("42");  // 42

`parseFloat()` - Converts string to float

let n = parseFloat("3.14"); // 3.14

`Number()` - Converts any type to number

Number("10")      // 10
Number(true)      // 1
Number("abc")     // NaN

`isNaN()` - Is Not a Number?

console.log(isNaN("abc")); // true
console.log(isNaN(123));   // false

Dealing with Decimals

Sometimes floating-point math can be imprecise:

console.log(0.1 + 0.2); // 0.30000000000000004 😕

You can fix it using toFixed():

let total = (0.1 + 0.2).toFixed(2); // "0.30" (as a string)

Number Methods

Method	Description	Example
`toFixed(n)`	Rounds to `n` decimal places	`(3.14159).toFixed(2)` → `"3.14"`
`toString()`	Converts number to string	`(100).toString()` → `"100"`
`typeof`	Checks if it's a number	`typeof 42` → `"number"`

🧪 Practice Exercise:

Task:

Write a program that adds, subtracts, multiplies and divides two numbers.
Generate a random number between 1 and 100.
Round 4.675 to 2 decimal places using toFixed().
Convert "123.45" to a number and multiply it by 2.
Get the square root of any number using Math.sqrt().

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