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 15
:
document.write(13 + 2)
The following sections introduce 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 132).
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 133 lists the various assignment operators available.
Operator  Example  Equivalent to 

 

 

 

 


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