AJAX - The Complete Reference

PART IV

Appendix A: JavaScript Quick Reference 575

Statements and Blocks

JavaScript statements are terminated either with a semicolon or an implied semicolon as

indicated by a return character. Thus:

var x = 5;

var y = 10;

and:

var x = 5

var y = 10

are equivalent. However, because of whitespace reflow, the second is clearly more

dangerous as it is sensitive to formatting.

We can group statements together in JavaScript using a block as indicated by enclosing

them in curly braces:

{

statements

}

where statements is composed of zero or more valid JavaScript statements. Statements can

always be grouped like this, as the body of a loop or function, or directly in the script,

although a block has only its own local scope for functions. However, we saw earlier, under

JavaScript 1.7 it is possible to create local bindings using a let statement.

Precedence Associativity Operator Operator Meanings

Left ==, !=, ===, !=== Equality, inequality, equality with

type checking, inequality with type

checking

Left & Bitwise AND

Left ^ Bitwise XOR

Left | Bitwise OR

Left && Logical AND

Left || Logical OR

Right? : Conditional

Right = Assignment

Right *=, /=, %=, +=, –=,

<<=, >>=, >>>=, &=,

^=, |=

Operation and self-assignment

Lowest Left , Multiple evaluation

TABLE A-18 Precedence and Associativity of JavaScript Operators (continued)