18 JavaScript Number Methods, Simplified examples

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October 31, 2022

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JavaScript

Introduction

The JavaScript number methods help you to work with numbers. JavaScript can work with various numeric values like integer, float, hexadecimal, decimal, exponential and octal values.

We will explain Javascript number methods in a simple manner with examples.

The toString() method.

This method converts the number into a string or returns a number as a string.

var x = 123;

// x is number
console.log(typeof(x));
//output: "number"

var y = x.toString()

// convert to string
console.log(typeof(y));
//output: "string"

The toExponential() Method

Exponential notation is a method of writing numbers.

Exponential numbers take the form Xⁿ, where X is multiplied by itself n times.

A simple example is 8 = 2³ = 2×2×2.

In JavaScript toExponential() method returns a string with a rounded number written in exponential form.

var x = 323.34;
var y = x.toExponential();
console.log(y);
//output : 3.2334e+2

The toFixed() Method

The toFixed() method converts a given number into a string. It rounds to a specified number of decimals. Additional zeros are added to create the desired decimal length if the number of decimals is higher than the actual number.

var x = 323.3433;
var y = x.toFixed(2);
console.log(y);
//same as
//x.toFixed(0);           // returns 4
//x.toFixed(2);           // returns 3.66
//output: 323.34
//Example: if the given length in parameters is larger
var x = 3.656;
console.log(x.toFixed(4));
// output: 3.6560
console.log(x.toFixed(6));
//output:  3.656000

The toPrecision() Method

The toPrecision() method formats a number to a specified length with the given number of significant digits. It rounds the result where necessary. This method returns the value as a string.

Here is a simple example

var x = 7.938;
x.toPrecision();        // output 7.938
x.toPrecision(2);       // output 7.9
x.toPrecision(4);       // output  7.938
x.toPrecision(6);       // output 7.93800

The valueOf() Method

The valueOf() method returns the primitive value of a String object.

This method is called internally by JavaScript, and not explicitly in the code. All JavaScript data types have a valueOf() and a toString() method.

var x = 444;
x.valueOf();            // output 444 from variable x

How to convert String variables to Numeric in JavaScript?

There are 3 JavaScript methods that can be used to convert string variables to numbers.
Number() method, parseInt() method and parseFloat() method

JavaScript global methods

The methods mentioned above are JavaScript global methods. this includes:

Number() Method
parseInt() method
parseFloat() method

Number() Method

The Number() method is used to convert JavaScript variables to numbers.

consider the following example

// Example

Number(true);
// output: 1
Number(false);
// output: 0
Number("20");
// output: 20
Number(" 20  ");
// output: 20
Number("20.43");
// output: 20.43
Number("20,33"); 
// output:  NaN (Not a Number)
Number("20 33");
// output: NaN
Number("John Doe");
// output: NaN

//

The Number() method is also useful to convert Dates to numbers. It returns the number of milliseconds since 1-1-1970.

// Example

let dateToNumber  = Number(new Date("2021-01-01"));
console.log(dateToNumber);
// output: 1609459200000

//

parseInt() method

parseInt() parses a string and returns a whole number. Use spaces as parameters but it returns only the first number.

This method returns NaN ( not a number ) if the given string is impossible to convert to a number.

// Example

parseInt("20");
// output: 20
parseInt("20.73");
//output: 20
parseInt("20 70");
// output: 20
parseInt("20 Days");
// output: 20
parseInt("Date 20");
// output: NaN
 
//

parseFloat() Method

The parseFloat() Method in JavaScript parses a string and returns a floating-point number. It also returns NaN if the given string is impossible to convert to a string.

// Example

parseFloat("20");        
// output: 20
parseFloat("20.71");     
// output: 20.71
parseFloat("20 10");  
// output: 20
parseFloat("20 Days");  
// output: 20
parseFloat("Number 20");  
// output: NaN

//