# JavaScript Numbers

JavaScript has only one type of number. Numbers can be written with or without decimals.

### Example

```
let x = 3.14; // A number with decimals
```

let y = 3; // A number without decimals

Extra large or extra small numbers can be written with scientific (exponent) notation:

## JavaScript Numbers are Always 64-bit Floating Point

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) |

## Integer Precision

Integers (numbers without a period or exponent notation) are accurate up to 15 digits.

### Example

```
let x = 999999999999999; // x will be 999999999999999
```

let y = 9999999999999999; // y will be 10000000000000000

Try it Yourself »
The maximum number of decimals is 17.

## Floating Precision

To solve the problem above, it helps to multiply and divide:

```
let x = (0.2 * 10 + 0.1 * 10) / 10;
```

Try it Yourself »
## Adding Numbers and Strings

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:

If you add two strings, the result will be a string concatenation:

If you add a number and a string, the result will be a string concatenation:

If you add a string and a number, the result will be a string concatenation:

A common mistake is to expect this result to be 30:

A common mistake is to expect this result to be 102030:

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.

## Numeric Strings

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 - Not a Number

`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 is numeric, the result will be a number:

You can use the global JavaScript function `isNaN()`

to find out if a value is a not a number:

Watch out for `NaN`

. If you use `NaN`

in a mathematical operation, the result will also be `NaN`

:

Or the result might be a concatenation like NaN5:

`NaN`

is a number: `typeof NaN`

returns `number`

:

## Infinity

`Infinity`

(or `-Infinity`

) is the value JavaScript will return if you calculate a number outside the largest
possible number.

### Example

```
let myNumber = 2;
```

// Execute until Infinity

while (myNumber != Infinity) {

myNumber = myNumber * myNumber;

}

Try
it Yourself »Division by 0 (zero) also generates `Infinity`

:

`Infinity`

is a number: `typeof Infinity`

returns `number`

.

## Hexadecimal

JavaScript interprets numeric constants as hexadecimal if they are preceded by 0x.

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**.

### Example

```
let myNumber = 32;
```

myNumber.toString(32);

myNumber.toString(16);

myNumber.toString(12);

myNumber.toString(10);

myNumber.toString(8);

myNumber.toString(2);

Try it Yourself »
## JavaScript Numbers as Objects

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);
```

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);

Try it Yourself »
When using the `===`

operator, x and y are **not equal**.

```
let x = 500;
```

let y = new Number(500);

Try it Yourself »
Note the difference between `(x==y)`

and `(x===y)`

.

Comparing two JavaScript objects **always** returns **false**.

## Complete JavaScript Number Reference

For a complete Number reference, visit our:

Complete JavaScript Number Reference.

The reference contains descriptions and examples of all Number properties and methods.