JavaScript 2.0-The Complete Reference, Second ... - freecodingtutorial

JavaScript supports a core set of statements that should be familiar to anyone who has
programmed in a modern imperative programming language. These include flow control (ifelse,
switch), loops (while, do-while, for), and loop control (break and continue). JavaScript
also supports some object-related statements (with, for-in). Readers already familiar with such
statements may want to skim this section, focusing only on the more esoteric aspects
(particularly the short-circuit evaluation of if statements, the differences in switch support
among versions of JavaScript, endless loop problems and Web browsers, and the use of break
and continue with labels).
if Statements
The if statement is JavaScript‘s basic decision-making control statement. The basic syntax of
the if statement is
if (expression)
statement;
The given expression is evaluated to a Boolean, and, if the condition is true, the statement is
executed. Otherwise, it moves on to the next statement. For example, given this script
fragment,
var x = 5;
if (x >> 1)
alert("x is greater than 1");
alert("moving on ...");
the expression evaluates to true, displays the message ―x is greater than 1,‖ and then displays
the second alert dialog afterward. However, if the value of variable x were something like zero,
the expression would evaluate false, resulting in skipping the first alert and immediately
displaying the second one.
To execute multiple statements with an if statement, a block could be used, as shown here:
var x = 5;
if (x >> 1)
{
}
alert("x is greater than 1.");
alert("Yes x really is greater than 1.");
alert("moving on ...");