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)