HTML tutorial
CSS3 tutorial
Bootstrap tutorial
JavaScript tutorial
JQuery tutorial
AngularJS tutorial
React tutorial
NodeJS tutorial
PHP tutorial
Python tutorial
Python3 tutorial
Django tutorial
Linux tutorial
Docker tutorial
Ruby tutorial
Java tutorial
C tutorial
C ++ tutorial
Perl tutorial
JSP tutorial
Lua tutorial
Scala tutorial
Go tutorial
ASP.NET tutorial
C # tutorial
JavaScript has only one type of number.Numbers can be written with or without decimals
Unlike many other programming languages, JavaScript does not define different types of numbers, like integers, short, long, floating-point etc.
JavaScript numbers are always stored as double precision floating point
numbers, following the international IEEE 754 standard.
This format
stores numbers in 64 bits, where the number (the fraction) is stored in bits 0
to 51, the exponent in bits 52 to 62, and the sign in bit 63:
Value (aka Fraction/Mantissa) | Exponent | Sign |
---|---|---|
52 bits (0 - 51) | 11 bits (52 - 62) | 1 bit (63) |
Integers (numbers without a period or exponent notation) are accurate up to 15 digits.
let x = 999999999999999; // x will be 999999999999999
let y = 9999999999999999; // y will be 10000000000000000
The maximum number of decimals is 17.
To solve the problem above, it helps to multiply and divide:
let x = (0.2 * 10 + 0.1 * 10) / 10;
WARNING !!
JavaScript uses the + operator for both addition and concatenation.
Numbers are added. Strings are concatenated.
If you add two numbers, the result will be a number:
let x = 10;
let y = 20;
let z = x + y;
If you add two strings, the result will be a string concatenation:
let x = "10";
let y = "20";
let z = x + y;
If you add a number and a string, the result will be a string concatenation:
let x = 10;
let y = "20";
let z = x + y;
If you add a string and a number, the result will be a string concatenation:
let x = "10";
let y = 20;
let z = x + y;
A common mistake is to expect this result to be 30:
let x = 10;
let y = 20;
let z = "The result is: " + x + y;
A common mistake is to expect this result to be 102030:
let x = 10;
let y = 20;
let z = "30";
let result = x + y + z;
The JavaScript interpreter works from left to right.
First 10 + 20 is added because x and y are both numbers.
Then 30 + "30" is concatenated because z is a string.
JavaScript strings can have numeric content:
let x = 100; // x is a number
let y = "100"; // y is a
string
JavaScript will try to convert strings to numbers in all numeric operations:
This will work:
let x = "100";
let y = "10";
let z = x / y;
This will also work:
let x = "100";
let y = "10";
let z = x * y;
And this will work:
let x = "100";
let y = "10";
let z = x - y;
But this will not work:
let x = "100";
let y = "10";
let z = x + y;
In the last example JavaScript uses the + operator to concatenate the strings.
NaN
is a JavaScript reserved word indicating that a number is not a legal number.
Trying to do arithmetic with a non-numeric string will result in NaN
(Not a
Number):
However, if the string contains a numeric value , the result will be a number:
let x = 100 / "10";
You can use the global JavaScript function isNaN()
to find out if a value is a not a number:
let x = 100 / "Apple";
isNaN(x);
Watch out for NaN
. If you use NaN
in a mathematical operation, the result will also be NaN
:
let x = NaN;
let y = 5;
let z = x + y;
Or the result might be a concatenation like NaN5:
let x = NaN;
let y = "5";
let z = x + y;
NaN
is a number: typeof NaN
returns number
:
typeof NaN;
Infinity
(or -Infinity
) is the value JavaScript will return if you calculate a number outside the largest
possible number.
let myNumber = 2;
// Execute until Infinity
while (myNumber != Infinity) {
myNumber = myNumber * myNumber;
}
Division by 0 (zero) also generates Infinity
:
let x = 2 / 0;
let y = -2 / 0;
Infinity
is a number: typeof Infinity
returns number
.
typeof Infinity;
JavaScript interprets numeric constants as hexadecimal if they are preceded by 0x.
let x = 0xFF;
Never write a number with a leading zero (like 07).
Some JavaScript versions interpret
numbers as octal if they are written with a leading zero.
By default, JavaScript displays numbers as base 10 decimals.
But you can use the toString()
method to output numbers from base 2
to base 36.
Hexadecimal is base 16. Decimal is base 10. Octal is base 8. Binary is base 2.
let myNumber = 32;
myNumber.toString(32);
myNumber.toString(16);
myNumber.toString(12);
myNumber.toString(10);
myNumber.toString(8);
myNumber.toString(2);
Normally JavaScript numbers are primitive values created from literals:
let x = 123;
But numbers can also be defined as objects with the keyword new
:
let y = new Number(123);
let x = 123;
let y = new Number(123);
Do not create Number objects.
The new
keyword complicates the code and slows down execution speed.
Number Objects can produce unexpected results:
When using the ==
operator, x and y are equal:
let x = 500;
let y = new Number(500);
When using the ===
operator, x and y are not equal.
let x = 500;
let y = new Number(500);
Note the difference between (x==y)
and (x===y)
.
(x == y)
true or false?
let x = new Number(500);
let y = new Number(500);
(x === y)
true or false?
let x = new Number(500);
let y = new Number(500);
Comparing two JavaScript objects always returns false.
For a complete Number reference, visit our:
Complete JavaScript Number Reference.
The reference contains descriptions and examples of all Number properties and methods.