Javascript Number Properties And Methods

In this tutorial, you will learn how numbers are handled in JavaScript. You will learn about different mathematical operations on numbers, how to convert numbers to strings, how to round numbers, how to format numbers, and how to convert strings to numbers.

JavaScript Number

In javascript, the Number is a primitive data type. It represents all numerical values like:

1. Integer - 2, 5, 18, 100, 55, etc
2. Float - 1.0, 2.5, 8.4503, 245.50, etc
3. Exponential - 1.23e5, 1.23e-5, etc
4. Binary - 0b1010, 0b1111, etc
5. Octal - 0o7, 0o77, 0o777, etc
6. Hexadecimal - 0xFF, 0xFFF, 0xFFFF, etc
7. etc

The numbers in javascript is always stored in double-precision floating-point numbers means it can store both integral and fractional values.

There are two ways to define numbers in javascript:

1. Number literals - Like 10, 25, 45, etc
2. Number Constructor - It can convert any string or other data type to a number. If it is not convertible to a number then it gets converted to NaN.

Generally, browsers automatically convert Number literals to instances of Number class.

// Number literals
const num1 = 15;
const num2 = 12.55;
console.log(num1, typeof num1);
console.log(num2, typeof num2);

// Number constructor
const num3 = Number(15);
const num4 = Number(12.55);
console.log(num3, typeof num3);
console.log(num4, typeof num4);

Creating Javascript Number Using Constructor

To create a number using number constructor use Number() as function/constructor and pass the number as an argument. Example Number(20), Number(35.5), Number('12') etc.

const num1 = Number(15);
const num2 = Number(12.55);
console.log(num1, typeof num1);
console.log(num2, typeof num2);

// Convert string to number
console.log('1250');

Ways to write a number in Javascript

Generally, we write numbers in decimal format. But there are some ways to write numbers in javascript.

1. Decimal method
2. Exponential method
3. Other Number System

1. Decimal Method

The number system that we use in our daily life is the decimal number system. Numbers in the decimal number system ranges from 0-9. Defining numbers using a combination of 0-9 is a decimal number.

const num1 = 50;
const num2 = 12.54;
console.log(num1, num2);

2. Exponential Method

While writing numbers like 1 billion or 1 trillion in numbers we would have to write like 100000000 and 10000000000 respectively, which is very inconvenient.

Javascript provides a method to write such numbers in an easier manner. We can shorten the number by appending 'e' or 'E' to the number and then specifying the number of 0's after it. Example, 1000 can be written as 1e3, 0.002 as 2e-3, 50000 as 5e4 etc. This is the exponential method of writing numbers.

const num1 = 23e2;
console.log(num1);

const num2 = 1e7;
console.log(num2);

const num3 = 123456e-3;
console.log(num3);

const num4 = 0.00234e10;
console.log(num4);

const num5 = 99545e-9;
console.log(num5);

3. Other Number System

There exist other number systems apart from decimal number systems like binary, octal, hexadecimal, etc.

hexadecimal numbers are widely used in the hex color system.

The hexadecimal number is defined by the suffix 0x in the number. example 0xff, 0x25, etc.

const num1 = 0xff;
const num2 = 0xFF; // case doent't matter -- 255
const num3 = Number(0x22);
const num4 = Number(0x1e2);
console.log(num1, num2, num3, num4);

Binary numbers include only 2 different numbers, 0's and 1's. It is defined by adding the suffix 0b in the number. example 0b1010, 0x11 etc.

const num1 = 0b1111;
const num2 = 0b1010;
const num3 = Number(0b1000001);
const num4 = Number(0b111110001);
console.log(num1, num2, num3, num4);

Octal numbers includes 8 different digits in their numbers 0,1,2,3,4,5,6 and 7. It is defined by adding the suffix 0o in the number. example 0o45, 0o22 etc.

const num1 = 0o7;
const num2 = 0o45;
const num3 = Number(0o30);
const num4 = Number(0o255);
console.log(num1, num2, num3, num4);

Javascript Number Properties

Number is a global object in javascript, it has many properties.

All the properties of Number are static like properties of math.

console.log(Number.EPSILON);
console.log(Number.MAX_VALUE);
console.log(Number.MAX_SAFE_INTEGER);
console.log(Number.MIN_VALUE);
console.log(Number.MIN_SAFE_INTEGER);
console.log(Number.NaN);
console.log(Number.NEGATIVE_INFINITY);
console.log(Number.POSITIVE_INFINITY);

Javascript Number methods

Number methods in javascript help us to work with numbers. A primitive value such as 2, 18, etc can't have properties and methods but when we call methods on these values javascript treats it as an object.

1. isNaN()
2. isFinite()
3. isInteger()
4. isSafeInteger()
5. parseFloat()
6. parseInt()
7. toExponential()
8. toFixed()
9. toLocalString()
10. toPrecision()
11. toString()
12. valueOf()

1. isNaN In Javascript

The isNaN() method is a global function that determines whether the given value is NaN (Not A Number) or not. If the passed value is NaN then it returns true else returns false.

You can alternatively also use Number.isNaN.

Why do we need the isNaN method?

Unlike other values in javascript, we can't compare a NaN value with another NaN. Since both NaN == NaN and NaN === NaN are false. Hence, we need the isNaN method to check whether a number is NaN or not.

console.log(isNaN(NaN));
console.log(isNaN(10));
console.log(isNaN("abc"));
console.log(isNaN());

2. isFinite In Javascript

The isFinite() method is a global function that determines whether the given value is a finite number or not. The passed value is also converted to a number if it is possible.

If the passed value is either NaN, positive infinity, or negative infinity then this method returns false else return true.

console.log(isFinite(100));
console.log(isFinite(1000));
console.log(isFinite("abc"));
console.log(isFinite("20"));
console.log(isFinite(NaN));
console.log(isFinite(Infinity));
console.log(isFinite(-Infinity));

3. isInteger In Javascript

The isInteger() method determines whether the given value is an integer or not.

If the passed value is either NaN, positive infinity or negative infinity then this method returns false and returns true for numbers.

console.log(Number.isInteger(10));
console.log(Number.isInteger(Math.PI));
console.log(Number.isInteger(22.15));
console.log(Number.isInteger(-25));
console.log(Number.isInteger(true));
console.log(Number.isInteger(NaN));
console.log(Number.isInteger(Infinity));
console.log(Number.isInteger(-Infinity));

4. isSafeInteger In Javascript

The isSafeInteger() method determines whether the given value is a safe integer or not.

A safe integer is a number that can be exactly represented as an IEEE-754 double-precision number ie. all integers from -(2⁵³ - 1) to (2⁵³ - 1).

The isSafeInteger() method returns true if the value is of type Number and is a safe integer.

console.log(Number.isSafeInteger(10));
console.log(Number.isSafeInteger(Math.PI));
console.log(Number.isSafeInteger(Math.pow(2, 53) - 1));
console.log(Number.isSafeInteger(-(Math.pow(2, 53) - 1)));
console.log(Number.isSafeInteger(Math.pow(2, 53)));
console.log(Number.isSafeInteger(NaN));
console.log(Number.isSafeInteger(Infinity));

5. parseFloat In Javascript

The Number.parseFloat() or parseFloat() method parses an argument and returns a floating-point number. If the number can't be parsed then it returns NaN.

You can use it to take out numerial values from real life units like "55kg", "120px", "220km", etc.

If the first character can not be converted to a number then it returns NaN.

console.log(parseFloat("55kg"));
console.log(parseFloat("125.55px"));
console.log(parseFloat("abc"));

6. parseInt In Javascript

The Number.parseInt() or parseInt() method is same as parseFloat method but it only extracts integer value from the passed value.

parseInt also accepts an optional argument which is radix (the base in a mathematical number system).

If the first character can not be converted to a number then it returns NaN.

console.log(parseInt("55kg"));
console.log(parseInt(127.0234));
console.log(parseInt("a100"));

7. toExponential Method In Javascript

The Number.toExponential() method converts numbers into exponential notation and returns them as a string.

This method accepts an optional argument which is an integer that specifies the number of digits after the decimal value.

const num1 = 53455;
const num2 = 8362926;
console.log(num1.toExponential());
console.log(num2.toExponential(5));
console.log(Number.parseInt(3929).toExponential());

8. toFixed Method In Javascript (round number)

The Number.toFixed() method in javascript formats the passed number using fixed-point notation. It is used to format a number with any specific number of digits.

Number.toFixed() method has a number argument that specifies the number of digits after decimal point

This method round of numbers as in maths.

const num1 = 5.3455;
const num2 = 8.36499;
console.log(num1.toFixed());
console.log(num2.toFixed(2));
console.log(Number.parseFloat(3.929).toFixed(2));

9. toLocaleString Method In Javascript (format number)

The Number.toLocaleString() method converts a Date object to a string using locale conventions.

It accepts an argument called locale used to get locale date for the country. Example en-AU (Australian English), en-IN (Indian English), bn-IN (Bangla India), etc.

const today = new Date();
console.log(today.toLocaleString('en-AU'));
console.log(today.toLocaleString('en-IN'));
console.log(today.toLocaleString('bn-IN'));

10. toPrecision Method In Javascript

The Number.toPrecision() method changes the number's precise value up to the passed number and returns the number as a string. Example: 125000's precision is 3.

This method accepts a number as an argument that defines precision.

const num1 = 123456;
const num2 = 34.52353;
console.log(num1.toPrecision(3));
console.log(num2.toPrecision(4));

11. toString Method In Javascript (number to string)

The Number.toString() method returns a string representing the number which invoked it.

This method accepts an optional argument that represents the base of the number system. If you pass 2 then the number will be converted to binary format and returned as a string. Its default value is 10.

const num1 = 100;
const num2 = 8;
console.log(num1.toString(16));
console.log(num1.toString(8));
console.log(num2.toString(2));

12. valueOf Method In Javascript

The Number.valueOf() method returns a primitive number for the specified object.

const num1 = new Number(25);
console.log(num1.valueOf());
console.log(typeof num1.valueOf(), typeof num1);

Conclusion

JavaScript Number object hold multiple properties and methods. The properties hold some important constants to be used in javascript while dealing with numbers. The methods are of different types static and instance methods.