Number Methods in JavaScript

2 min
Beginner

Properties of the Number Type

The Number object provides several useful properties.

Constant	Description
`Number.MAX_VALUE`	The largest number that can be represented.
`Number.MIN_VALUE`	The smallest positive number that can be represented.
`Number.NEGATIVE_INFINITY`	Represents the negative infinity value.
`Number.POSITIVE_INFINITY`	Represents the positive infinity value.
`Number.NaN`	Represents a value that is “Not-a-Number”.

console.log(Number.MAX_VALUE); // 1.7976931348623157e+308
console.log(Number.MIN_VALUE); // 5e-324
console.log(Number.NaN); // NaN

Methods of the Number Type

The Number object provides a variety of methods for working with numbers. Let’s look at some of the most useful ones.

Conversion Methods

Method	Description
`toString()`	Converts the number to a string.
`toFixed()`	Formats the number using fixed-point notation and returns a string
`toExponential()`	Converts the number to a string in exponential notation
`toPrecision()`	Formats the number to a string with the specified number of significant digits.

toFixed()

The Number.toFixed() method formats a number using fixed-point notation. It allows you to specify the number of decimals.

let num = 123.456789;

console.log(num.toFixed(2)); // '123.46'
console.log(num.toFixed(5)); // '123.45679'

toExponential()

The Number.toExponential() method returns a string representing the number in scientific notation.

let num = 123456;

console.log(num.toExponential()); // '1.23456e+5'
console.log(num.toExponential(2)); // '1.23e+5'

toPrecision()

The Number.toPrecision() method formats a number to a specific number of digits of precision.

let num = 123.456789;

console.log(num.toPrecision(4)); // '123.5'
console.log(num.toPrecision(7)); // '123.4568'

Method	Description
`parseInt()`	Converts a string to an integer
`parseFloat()`	Converts a string to a floating-point number

parseInt()

The Number.parseInt() method converts a string to an integer. An optional numeric base can be specified (such as binary, octal, decimal, hexadecimal).

console.log(Number.parseInt('101')); // 101
console.log(Number.parseInt('101', 2)); // 5 (binary to decimal)
console.log(Number.parseInt('10.5')); // 10

parseFloat()

The Number.parseFloat() method converts a string to a floating-point number. This is useful for interpreting and handling input data in text format.

console.log(Number.parseFloat('3.14')); // 3.14
console.log(Number.parseFloat('10.5abc')); // 10.5
console.log(Number.parseFloat('abc10.5')); // NaN

Sign and Comparison Methods

Method	Description
`isInteger()`	Determines whether the value is an integer
`isNaN()`	Determines whether the value is `NaN`
`isFinite()`	Determines whether the value is a finite number

isInteger()

The isInteger() method determines whether the passed value is an integer. This includes numbers without a decimal part.

console.log(Number.isInteger(42)); // true
console.log(Number.isInteger(42.5)); // false
console.log(Number.isInteger('42')); // false

isNaN()

Determines whether the value is NaN.

console.log(Number.isNaN(NaN)); // true
console.log(Number.isNaN(5)); // false

isFinite()

The isFinite() method determines whether the passed value is a finite number. This is useful for checking if a value is a number and not infinite.

console.log(Number.isFinite(42)); // true
console.log(Number.isFinite(Infinity)); // false
console.log(Number.isFinite('42')); // false