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hexadecimal literal

directly (not accessed from another variable). For example, the following line of code declares a variable

to hold an integer value, which is defined by the literal

var iNum = 55;

Integers can also be represented as either octal (base 8) or hexadecimal (base 16) literals. For an octal lit-

eral, the first digit must be a zero (0), and the following digits can be any octal digit (0 through 7), as in

this line of code:

var iNum = 070; //070 is equal to 56 in decimal

To create a hexadecimal literal, the first digit must be a zero (0) followed by the letter x, followed by any

number of hexadecimal digits (0-9 and A-F). The digits may be in uppercase or lowercase. For example:

var iNum = 0x1f; //0x1f is equal to 31 in decimal

var iNum2 = 0xAB; //0xAB is equal to 171 in decimal

To define a floating-point value, you must include a decimal point and one digit after the decimal point

(for instance, use 1.0 not 1.). This is considered a floating-point number literal. Example:

var fNum = 5.0;

The interesting thing about this form of floating-point literal is that it is actually stored as a string until

it’s needed for calculation.

For very large or very small numbers, floating-point values can be represented using

e-notation

. In

e-notation, a number is represented by digits (including decimal digits), followed by an

(or an

followed by the number of times to multiply it by 10. Confused? Here’s an example:

var fNum = 3.125e7;

This notation represents the number 31250000. You can get this value by converting the e-notation to a

calculation: 3.125

, which is exactly equal to 3.125

10.

E-notation can also be used to represent very small numbers, such as 0.00000000000000003, which can be

written as 3e-17 (here, 10 is raised to the –17 power, meaning that you will actually be dividing by 10 17

times). ECMAScript, by default, converts any floating-point number with six or more leading zeros into

e-notation.

Floating-point values are stored in a 64-bit IEEE 754 format, meaning that decimal

values can have up to 17 decimal places. After that, the values are truncated, result-

ing in small mathematical errors.

Even though integers can be represented as octal and hexadecimal literals, all mathe-

matical operations return decimal results.

ECMAScript Basics

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