HTML and CSS Reference
InDepth Information
chapter
Operators
and Expressions
Data objects can be manipulated in a number of ways by the large number of operators
provided by JavaScript. Operators are symbols, such as +, , =, >, and <, that produce a
result based on some rules. An operator manipulates data objects called operands; for
example,
5
and
4
are operands in the expression
5 + 4
. Operators and operands are found
in expressions. An expression combines a group of values to make a new value,
n = 5 + 4
.
And when you terminate an expression with a semicolon or a newline, you have a com
plete statement (e.g.,
n = 5 + 4;
).
var sum
=
5
+
4
new variable
operator
operand
operator
operand
In the numeric
expression
,
5 + 4  2
, three numbers are combined. The
operators
are
the + and  signs. The
operands
for the + sign are
5
and
4
. After that part of the expres
sion is evaluated to
9
, the expression becomes
9

2
. After evaluating the complete
expression, the result is
7
. Because the plus and minus operators each manipulate two
operands, they are called binary operators. If there is only one operand, the operator is
called a unary operator. If there are three operands, it is called a ternary operator. We'll
see examples of these operators later in the chapter.
The operands can be either strings, numbers, Booleans, or a combination of these. We
have already used some of the operators: the concatenation operator to join two strings
together, the
typeof
operator to determine what data type is being used, and the assign
ment operator used to assign a value to a variable. Now let's look at a plethora of addi
tional JavaScript operators and see how they manipulate their operands.
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