JavaScript Numbers & Math¶

JavaScript Numbers¶

JavaScript has only one type of number. Numbers can be written with, or without decimals.

let x = 3.14;    // A number with decimals
let y = 3;       // A number without decimals

Integers are accurate up to 15 digits. Floating point arithmetic is not always 100% accurate:

let x = 0.2 + 0.1; // 0.30000000000000004

Fix: To solve this, multiply and divide: let x = (0.2 * 10 + 0.1 * 10) / 10;

NaN is a reserved word indicating that a number is not a legal number.

let x = 100 / "Apple"; // x is NaN
console.log(isNaN(x));  // true

toString(): Returns a number as a string.
toFixed(n): Returns a string with the number written with n decimals (e.g., 9.656.toFixed(2) -> "9.66").
Number(str): Converts a variable to a number.
parseInt(str): Parses a string and returns a whole number.

The JavaScript Math object allows you to perform mathematical tasks on numbers.

Method	Description
`Math.round(x)`	Rounds to the nearest integer.
`Math.ceil(x)`	Rounds up to the nearest integer.
`Math.floor(x)`	Rounds down to the nearest integer.
`Math.sqrt(x)`	Returns the square root.
`Math.abs(x)`	Returns the absolute value.
`Math.random()`	Returns a random number between 0 and 1.

Math.ceil(4.4); // 5
Math.floor(4.7); // 4

Random Integer

To get a random integer between 0 and 10: Math.floor(Math.random() * 11);