Possible Duplicate:
++someVariable Vs. someVariable++ in Javascript
I know you can add one to a variable simply by doing i++ (assuming i is your variable). This can best be seen when iterating through an array or using it in a "for" statement. After finding some code to use online, I noticed that the for statement used ++i (as apposed to i++).
I was wondering if there was any significant difference or if the two are even handled any differently.
Yes there is a big difference.
var i = 0;
var c = i++; //c = 0, i = 1
c = ++i; //c = 2, i = 2
//to make things more confusing:
c = ++c + c++; //c = 6
//but:
c = c++ + c++; //c = 13
And here is a fiddle to put it all together: http://jsfiddle.net/maniator/ZcKSF/
The value of ++i is i + 1 and the value of i++ is just i. After either has evaluated, i is i + 1. It's a difference in timing, which is why they're often called 'pre-increment' and 'post-increment'. In a for loop, it rarely matters, though.
People like Douglas Crockford advise not to use that way of incrementing, amongst other reasons because of what Rafe Kettler described. No matter how experienced you are, sometimes ++i/i++ will suprise you. The alternative is to simply add 1 to i using i += 1, readable, understandable and unambiguous.
have a look at this link : http://www.w3schools.com/js/js_operators.asp it's post increment versus pre increment. They both end up incrementing the value but one returns the value BEFORE incrementing (++y) and the other one returns the value AFTER (y++). However, it doesn't make any difference when using it in a for loop --
for( var i = 0; i < 100; i++ ) { ... }
is the same as
for( var i = 0; i < 100; ++i ) { ... }
a=1;
b=1;
c=++a;//the value of a is incremented first and then assigned to c
d=b++;//the value of b is assigned to d first then incremented
now if you print a,b,c,d..the output will be:
2 2 2 1
++i is called pre-increment and i++ is called post-increment. The difference is when the variable is incremented. Pre-incrementing a variable usually adds 1 and then uses that value, while post-incrementation uses the variable and then increments.
