Webmaster in a Nutshell, Second Edition

Expressions and Operators

JavaScript expressions are formed by combining literal values and variables with JavaScript operators. Parentheses can be used in an expression to group subexpressions and alter the default order of the evaluation of the expression. Here’s an example:

1+2
total/n
sum(o.x, a[3])++
(1+2)*3

JavaScript defines a complete set of operators, most of which should be familiar to all C, C++, and Java programmers. In Table 11.1, the P column specifies operator precedence and the A column specifies operator associativity: L means left-to-right associativity, and R means right-to-left associativity.

Table 11-1. Expressions and Operators

P	A	Operator	Operation Performed
15	L	.	Access an object property
	L	[]	Access an array element
	L	()	Invoke a function
14	R	++	Unary pre- or post-increment
	R	- -	Unary pre- or post-decrement
	R	-	Unary minus (negation)
	R	~	Numeric bitwise complement
	R	!	Unary boolean complement
	R	delete	Undefine a property (1.2)
	R	new	Create a new object
	R	typeof	Return type of operand (1.1)
	R	void	Return undefined value (1.1)
13	L	*, /, %	Multiplication, division, modulo
12	L	+, -	Addition, subtraction
	L	+	String concatenation
11	L	<<	Integer shift left
	L	>>	Shift right, sign extension
	L	>>>	Shift right, zero extension
10	L	<, <=	Less than, less than or equal
	L	>, >=	Greater than, greater than or equal
9	L	==, !=	Test for equality or inequality
	L	===, !==	Test for identity or nonidentity (no type conversion)
8	L	&	Integer bitwise AND
7	L	^	Integer bitwise XOR
6	L	|	Integer ...