Operators in JavaScript, as in PHP, can involve mathematics,
changes to strings, and comparison and logical operations (and
, or
,
etc.). JavaScript mathematical operators look a lot like plain
arithmetic; for instance, the following statement outputs 16:
document.write(14 + 2)
The following sections teach you about the various operators.
Arithmetic operators are used to perform mathematics. You can use them for the main four operations (addition, subtraction, multiplication, and division) as well as to find the modulus (the remainder after a division) and to increment or decrement a value (see Table 142).
Operator  Description  Example 
 Addition 

 Subtraction 

 Multiplication 

 Division 

 Modulus (division remainder) 

 Increment 

 Decrement 

The assignment operators are used to assign values to variables.
They start with the very simple, =
,
and move on to +=
, =
, and so on. The operator +=
adds the value on the right side to the
variable on the left, instead of totally replacing the value on the
left. Thus, if count
starts with
the value 6, the statement:
count += 1
sets count
to 7, just like
the more familiar assignment statement:
count = count + 1
Table 143 lists the various assignment operators available.
Operator  Example  Equivalent to 




















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