JavaScript Number Methods: A Complete Guide

Method	Description	Example
Number()	Convert string to a number	let str = "5"; Number(str) // 5
parseInt()	Convert string to a number	let str = "5"; parseInt(str) // 5 let str2 = "20px"; parseInt(str2) // 20
parseFloat()	Convert string to a float number	let str = "123.45"; parseFloat(str) // 123.45
toFixed()	Rounds to fixed decimals	let str = 3.14159; str.toFixed(2) // "3.14"
toPrecision()	Rounds to significant digits	let str = 3.14159; str.toPrecision(3) // "3.14"
isNaN()	Checks if value is NaN	let str = "hello"; isNaN(str) // true
isFinite()	Checks if a number is finite	let str = 42; isFinite(str) // true let str2 = 1/0; isFinite(str2) // false
Math Object	JavaScript has a built-in `Math` object for advanced operations:	console.log(Math.PI); // 3.14159 console.log(Math.round(4.7)); // 5 console.log(Math.floor(4.7)); // 4 console.log(Math.ceil(4.7)); // 5 console.log(Math.random()); // Random number between 0 and 1 like 0.123587

Number Conversion

Number() → Convert string to a number
parseInt() / parseFloat()

Example

let strNum = "123";

let num = Number(strNum); // 123

let intNum = parseInt(strNum); // 123

let floatNum = parseFloat("123.45"); // 123.45

console.log("5" - 2); // 3 (String "5" converted to number)

console.log("5" + 2); // "52" (2 converted to string)

Try it yourself

Rounds to decimals:

toFixed() → Round for fixed decimals
precision() → Round for significant digits

Example

3.14159.toFixed(2) // "3.14"

3.14159.toPrecision(3) // "3.14"

Try it yourself

Checking if a Value is a Number:

isNaN() | Number.isInteger() | Number.isFinite() → check if given value is number or not

Example

console.log(isNaN("Hello")); // true

console.log(Number.isInteger(42)); // true

console.log(Number.isFinite(42)); // true

Try it yourself

Math Object for Numbers:

JavaScript has a built-in Math object for advanced operations:

Example

console.log(Math.PI); // 3.14159

console.log(Math.round(4.7)); // 5

console.log(Math.floor(4.7)); // 4

console.log(Math.ceil(4.7)); // 5

console.log(Math.random()); // Random number between 0 and 1

Try it yourself

❮ Previous

Next ❯

Whereisstuff is simple learing platform for beginer to advance level to improve there skills in technologies.we will provide all material free of cost.you can write a code in runkit workspace and we provide some extrac features also, you agree to have read and accepted our terms of use, cookie and privacy policy.

Method

Description

Example

Number Conversion

Rounds to decimals:

Checking if a Value is a Number:

Math Object for Numbers: