Javascript will generally apply implicit conversions on operands as
required by operator used. The assignment operator (=) returns the
value of its right-side operand, and is right to left associative: so multiple
variables can be assigned the same value in one line:
a = b = c = 3;
In common with other languages, shortcut assignment-plus-operation operators
also exist: +=, -=, *=, /=, %=, <<=, >>=, >>>=, &=, |=, ^=
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Arithmetic Operators
| Operator |
Operation |
Notes |
| + |
addition or concatenation |
Adds numbers, concatenates strings. If one operator is a string, then
the other is converted to a string and concatenation is applied. Operator has left-to-right associativity |
| - |
subtraction |
|
| * |
multiplication |
|
| / |
division |
|
| % |
modulus division |
Returns the remainder
of dividing the left operand by the right operand |
| ++ |
increment |
|
| -- |
decrement |
|
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Comparison Operators
| Operator |
Operation |
Notes |
| == |
is equal to |
Equality tests will
generally allow type conversion to test for equality. "null" and
"undefined" are "equal" |
| === |
is identical to |
Both
operands must have type. For primitive datatypes, values must match. For
reference types, they must have the same reference. "null" is not identical
to "undefined" |
| != |
not equal to |
|
| !== |
not identical to |
|
| > |
greater than |
|
| >= |
greater than or equal to |
|
| < |
less than |
|
| <= |
less than or equal to |
|
| in |
is a property of |
evaluates to true if left string operand is a property of right
object operand |
| instanceof |
is an instance of |
evaluates to true if left object operand is an instance of the
right-side class operand |
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Logical and Bitwise Operators
| Operator |
Operation |
Notes |
|
&& |
Logical AND |
|
|| |
OR |
|
! |
Not |
| Sets bit to 1 if bit is
set to 1 in both left and right operand |
& |
Bitwise AND |
| Sets bit to 1 if bit is
set to 1 in either left and right operand |
| |
Bitwise OR |
| Sets bit to 1 if bit is
set to 1 in either left and right operand but not both |
| |
Bitwise XOR |
| Reverses all bits in its
argument |
~ |
Bitwise NOT |
| Shifts bits in left operand
to the left by the number specified in right operand. Equivalent to
multiplication by 2 to the power of right operand |
<< |
Shift left |
| Shifts bits in left
operand to the right by the number specified in right operand. Equivalent to
integer division by 2 to the power or right operand. Preserves sign of original
left operand |
>> |
Shift right |
| Shifts bits in left
operand to the right by the number specified in right operand. Fills left bits
with ones. Does not preserve sign of original left operand |
>>> |
Shift right |
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Miscellaneous Operators
| Operator |
Operation |
Notes |
| ?: |
Conditional |
The ternary operator |
| typeof |
datatype of operand |
Return value
can be one of "number", "string", "object", "boolean", "function", "undefined".
Returns "object" if operand == null. |
| new |
object constructor and initialiser |
Returns an object of type specified with optional parenthesised
argument list as initialisers |
| delete |
delete object property, array element or
variable |
Will not delete explicitly declared variables,
nor some built-in and client-side properties |
| void |
void |
discard operand value and return
"undefined". Typically used in client-side scripts, to evaluate an
expression for its side-effects, but avoid displaying the result on
the client browser |
| , |
comma |
Evaluates arguments left-to-right,
returns value of right argument |
| [] |
array element access |
|
| . |
object element access |
|
| () |
function call |
|
| in |
object property test |
if (x in o) then o.x = 1; |
A pop-up window using 'void':Open New Window"
