Learning PHP, MySQL, JavaScript, and CSS, 2nd Edition

Operators

JavaScript offers a lot of powerful operators, ranging from arithmetic, string, and logical operators to operators for assignment, comparison, and more (see Table 14-1).

Table 14-1. JavaScript operator types

Operator	Used for	Example
Arithmetic	Basic mathematics	a + b
Array	Array manipulation	a + b
Assignment	Assigning values	a = b + 23
Bitwise	Manipulating bits within bytes	12 ^ 9
Comparison	Comparing two values	a < b
Increment/Decrement	Adding or subtracting 1	a++
Logical	Boolean comparison	a && b
String	Concatenation	a + 'string'

Different types of operators take a different number of operands:

• Unary operators, such as incrementing ($a++) or negation (-$a), take a single operand.

• Binary operators, which represent the bulk of JavaScript operators (including addition, subtraction, multiplication, and division), take two operands.

• There is one ternary operator, which takes the form x ? y : z. It’s a terse, single-line if statement that chooses between two expressions, depending on the result of a third one. This conditional operator takes three operands.

Operator Precedence

Like PHP, JavaScript utilizes operator precedence, in which some operators in an expression are considered more important than others and are therefore evaluated first. Table 14-2 lists JavaScript’s operators and their precedences.

Table 14-2. The precedence of JavaScript operators (high to low)

Operator(s)	Type(s)
() [] .	Parentheses, call, and member
++ −−	Increment/decrement
+ − ~ !	Unary, bitwise, and logical
* / % ...