+= , -= , *= , /=
Perform a mathematical operation on a variable with another constant or variable. The += (et al) operators are just a convenient shorthand for the expanded syntax, listed below.
x += y; // equivalent to the expression x = x + y;
x -= y; // equivalent to the expression x = x - y;
x *= y; // equivalent to the expression x = x * y;
x /= y; // equivalent to the expression x = x / y;
x:
any variable type
y:
any variable type or constant
x = 2;
x += 4; // x now contains 6
x -= 3; // x now contains 3
x *= 10; // x now contains 30
x /= 2; // x now contains 15
