Arithmetic:
+
add
-
subtract
*
multiply
/
divide
%
modulus (remainder)
+
is also used to concatenate strings: s = "Hello " + name;
++
and --
increment and decrement by 1, commonly for loops:
x++; // Increment x (by 1)
a = x++ + y; // a = x + y, then increment x
b = --x * y; // Decrement x then b = x * y
Boolean operators:
&&
AND
||
OR
!
NOT
Comparisons:
==
is equal to
===
is identical to
!=
is not equal to
!==
is not identical to
>
is greater than
>=
is greater than or equal to
<
is less than
<=
is less than or equal to
The difference between being equal to and being identical to, we will see later.
Assignment:
=
(never to be confused with ==
or ===
)
We have already seen several examples. An expression is evaluated and the result is assigned to the variable on the left hand side:
x *= 3.14; // Shorthand for x = x * 3.14;
var paid = true;
var fullName = firstName + " " + lastName;
r2 = x * x + y * y;
var r = squareRoot (r2); // result from a function
NB: If nothing has yet been assigned to a variable declared with var
it has the special value undefined
.
The conditional operator: ? :
eg, var s = (x == y) ? firstName + " " : initial;
If the condition is true do the statement between ? and :, otherwise do the statement after the colon.
NB: Use this sparingly - it's hard to read
There are also compound operations of the form op=
+= -= *= /= %= &= |= ^= <<= >>= >>>=
eg,
a %= b; // is shorthand for:
a = a % b;