AJAX - The Complete Reference

PART IV

Appendix A: JavaScript Quick Reference 569

Arithmetic Operators

Arithmetic operators operate solely on numbers, with one exception, +, which is overloaded

and provides string concatenation as well. Table A-12 details the arithmetic operators found

in JavaScript.

Bitwise Operators

While JavaScript does not allow for standard C-like memory access, it does include bitwise

operators. Bitwise operators operate upon integers in a bit-by-bit fashion. Most computers store

negative numbers using their two’s complement representation, so you should exercise caution

when performing bit operations on negative numbers. Most uses of JavaScript rarely involve

bitwise operators, but they are presented in Table A-13 for those so inclined to use them.

Assignment Operators

Assigning a value to variable is performed using the = operator. There are a number of

shorthand notations in JavaScript that allow you to perform simple arithmetic or bitwise

operations and assign at the same time. These operators are shown in Table A-14.

Operator Operation Example

+ (unary) Has no effect on numbers but

causes non-numbers to be

converted into numbers

var x = +5;

var y = +"10";

// converted to 10

• (unary) Negation (changes the sign of
  the number or converts the
  expression to a number and
  then changes its sign)

var x = -10;

+ Addition (also functions as string

concatenation)

var sum = 5 + 8; // 13

• Subtraction var difference = 10 - 2; // 8

• Multiplication var product = 5 * 5; // 25

/ Division var result = 20 / 3; //

6.6666667

% Modulus (the remainder when

the first operand is divided by

the second)

alert(9.5 % 2); // 1.5

++ Auto-increment (increment the

value by one and store); may be

prefixed or postfixed but not both

var x = 5;

x++; // x now 6

−− Auto-decrement (decrement the

value by one and store); may be

prefixed or postfixed but not both

var x = 5;

x--; // x now 4

TABLE A-12 Arithmetic Operators