Numbers in JavaScript

JavaScript Numbers are dedicated to store the numeric values including integers, decimal values and exponential values as well. Numbers can hold positive as well as negative values.

  • There are no such separate categories for integers and decimal values in JavaScript. Both are treated as Numbers only.
    Example:
    var x = 25;
    var y = 2.5;​
  • Exponential values are used when you want to represent extremely large or small numbers. To write numbers in exponential form, letter e or E is used.
    Example:
    var z = 2.8333e10;
    This represents 2.8333 raised to the power 10.

How JavaScript Numbers are stored in memory?

In JavaScript, a number occupies 64 bits in the memory. This format is known as 64-bit floating point format defined by IEEE 754 standards. This format is also termed as Double Precision.

Let us see how these 64 bits are distributed to different parts of the number.

  1. 0 to 51st bit hold the integer or decimal value.
  2. 52nd to 62nd bit hold the exponential value.
  3. 63rd bit is dedicated for the sign, be it positive(+) or negative(-).

Since there is a limited amount of bits to store a number, therefore, only limited numbers can be represented in JavaScript. Maximum of 264 different numbers can be represented. Well, this is value is equivalent to 18 quintillions.

Range of Numbers in JavaScript

In JavaScript, the numbers must lie between -9007199254740992(-253) to 9007199254740992(253). A number going out of this range might lose its precision i.e the number won't be very accurate.

JavaScript Numbers as Objects

JavaScript Number is a primitive datatype but numbers can also be created as an object. For this purpose, a keyword new is used.

Syntax:
var variable_name = new Number(value);

Example:

<!DOCTYPE html>
<html lang="en">
 <head> </head>
 <body>
  <script>
   var age = new Number(56);
   document.write('age = ', age); 
  </script>
 </body>
</html>

Output:

age = 56

From the execution point of view, the number objects make the execution process very slow. Hence, they are avoided.

Special Numbers in JavaScript

JavaScript owns three special numbers. They are:

  1. Infinity
  2. -Infinity
  3. NaN

Infinity in JavaScript

It is the same infinity you've heard about in Mathematics. The positive infinity is displayed when the number falls above the range of floating point numbers i.e -1.797693134862315E+308 to 1.797693134862315E+308.

The most common example is 'Division by Zero' whose result is Infinity.
Example:

<!DOCTYPE html>
<html lang="en">
 <head> </head>
 <body>
  <script>
   var num_1 = 150;
   var num_2 = 0;
   document.write( num_1 / num_2 ); 
  </script>
 </body>
</html>

Output:

Infinity

-Infinity in JavaScript

Similar to infinity, negative infinity is displayed when a number falls below the range of floating-point numbers.

In this example, let us take a negative value as dividend.
Example:

<!DOCTYPE html>
<html lang="en">
 <head> </head>
 <body>
  <script>
   var num_1 = -150;
   var num_2 = 0;
   document.write( num_1 / num_2 ); 
  </script>
 </body>
</html>

Output:

-Infinity

NaN in JavaScript

NaN stands for 'Not a Number', which is displayed by JavaScript when a number is invalid. JavaScript does not generate an error in cases like 'Zero divided by Zero' or 'Number divided by String', instead, it gives NaN as output.

Let us see an example that shows what kind of values are NaN.
Example:

<!DOCTYPE html>
<html lang="en">
 <head> </head>
 <body>
  <script>
   document.write(0/0); //zero divided by zero.
   document.write(60/'ten'); //number divided by string. 
  </script>
 </body>
</html>

Output:

NaN
NaN