I'll admit. This concept is probably such a simple one that I shouldn't even be writing about it. But, I've fallen trap to this misconception many times — alas here I am typing.
So heres the problem...
Say you have
y which is the year, and you want to know what year next year is.
One may think to be terse and write:
var newYear = ++y;
Note: you may be tempted to use y++. But, y++ won't work here. Why you ask? Because of Prefix vs Postfix.
Perhaps only I am silly enough to write such things. Either way, you can probably spot the problem.
y are equal to
y + 1.
That makes for tricky use of
y later on.