Learning JavaScript

Chapter 3. Operators and Statements

The examples in the book so far have performed mostly simple tasks: a variable has been defined and its value set; a value is printed out in the page or in an alert window; a variable is modified through addition or multiplication or some other means. These all use JavaScript statements and operators.

There are a number of different types of statements in JavaScript: assignment, function call, conditional, and loops. Each is fairly intuitive, simple to use, and quick to learn. A snap, really. As with with most programming languages, in JavaScript the statements are easy to learn; the tricky part is lining them up, one after the other, so they do something useful.

This chapter takes a closer look at statements and operators, what they share, and how they differ.

Format of a JavaScript Statement

JavaScript statements terminate with a semicolon, though not all statements need the terminator expressly given. If the JavaScript engine determines that a statement is complete (whatever that is for each type of statement), and the line ends with a new line character, the semicolon can be omitted:

var bValue = true
var sValue = "this is also true"

If multiple statements are on the same line, though, the semicolon must be used to terminate each:

var bValue = true; var sValue = "this is also true";

However, not explicitly terminating each JavaScript statement is a bad habit to get into, and one that can result in unexpected consequences. As such, the use of the semicolon ...