Javascript - Number Number

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Introduction

ECMAScript Number uses the IEEE-754 format to represent both integers and floating-point values.

The most basic number literal format is a decimal integer, which can be entered directly as shown here: 

var intNum = 55;         //integer

Integers can be represented as either octal (base 8) or hexadecimal (base 16) literals.

For an octal literal, the first digit must be a zero (0) followed by a sequence of octal digits (numbers 0 through 7).

If a number out of this range is detected in the literal, then the leading zero is ignored and the number is treated as a decimal: 

var octalNum1 = 070;     //octal for 56 
var octalNum2 = 079;     //invalid octal - interpreted as 79 
var octalNum3 = 08;      //invalid octal - interpreted as 8

Octal literals are invalid when running in strict mode and will cause the JavaScript engine to throw a syntax error.

To create a hexadecimal literal, make the first two characters 0x (case insensitive), followed by any number of hexadecimal digits (0 through 9, and A through F).

Letters may be in uppercase or lowercase. Here's an example: 

var hexNum1 = 0xA;       //hexadecimal for 10 
var hexNum2 = 0x1f;      //hexedecimal for 31

Numbers created using octal or hexadecimal format are treated as decimal numbers in arithmetic operations.