Forum Moderators: open
Declare a variable, say
var x = 2;
If you want to increment it by one, you can use
x++; //x will be 3
If you want to increment it and assign the value to a new variable, then
y=++x; //y will be 3
As i said, the decrementing is the exact opposite, so
y=--x; //y will be 1
It's that simple
They are unary and conubial operators
var a = 9; Value (9) I understand this
var b = 0; Value (0) understand this too
b = a; Value (9) and understand this
b = ++a; Value (11) dont understand how this became 11
b = a++; Value (12) dont understand how this became 12
b = a++; Value (13) dont understand how this became 13
keep going over it, but still cant work it out. Unless this is wrong. Can you help?
<script type='text/javascript'>
var a = 9;
var b = 0;
b = a;
document.write('b now is: (b=a=>) ' + b+'<br />');
b = ++a;
document.write('b now is: (b=++a=>) ' + b+'<br />');
b = a++;
document.write('b now is: (b=a++=>) ' + b+'<br />');
b = a++;
document.write('b now is: (b=a++=>) ' + b+'<br />');
</script>
The result on win64 + Firefox 3 (but this really doesn't matter... well, shouldn't), is:
b now is: (b=a=>) 9
b now is: (b=++a=>) 10
b now is: (b=a++=>) 10
b now is: (b=a++=>) 11
Somebody, how can this be explained better?
[edited by: engine at 11:44 am (utc) on Jan. 12, 2009]
Well...What should I say?
I reproduced in the 5th post what you wrote in the third post. Copy/paste it in a HTML page's body and test it. If the results will match the results taken from the training CD i will call myself an idiot publicly on the Times Square because I couldn't copy/paste the results from my test page.
However in the case the results will not match the results taken from the CD, then I'll get a beer, savor a stake and state that I can copy/paste better than the creators of the CD.
I'd be quite interested of where did you get that Tutorial CD and who are the authors.
Somebody, how can this be explained better?
To take it a little further, let's take some var's for a loop and alert and see comments: (a and b were already beat to death, so I skipped them - lol)
var c = 0;
var d = 0;
var e = 0;
var f = 0;
var g = 0;
var h = 0;
var j = 0;
var k = 0;
var m = 0;
var n = 0;
for (var i = 0; i < 6; i++) {
c++; // c and d will be 6, value is being declared and evaluated instantly
++d;
f = e++; //f and h will be 5 because the increment evaluation occurs after f and h have been assigned a value
h = g; g++; //g will be 6, just like c and d, but h will be 5 because the increment of g happens after assignment of h's value, just like f
k = ++j; //k and j will both be 6, j is incremented first, then value assigned to k also
n = 1 + m++; //n and m will be 6, instead of n being 5 like f and h, because we cheated with the 1 + , without that, m would be 6 and n would be 5, just like f is 5 and e is 6
}
//c:6, d:6, e:6, f:5, g:6, h:6, j:6, k:6, m:6, n:6
alert("c: "+c+"\nd: "+d+"\ne: "+e+"\nf: "+f+"\ng: "+g+"\nh: "+h+"\nj: "+j+"\nk: "+k+"\nm: "+m+"\nn: "+n);
So what this shows really, is that incrementing when applied directly to a var is evaluated immediately. But, if assignment of value is being done using = the evaluation of the incrementing is done either before or after the assignment of value depending on whether the ++ is before or after the var being incremented.
//c:6, d:6, e:6, f:5, g:6, h:6, j:6, k:6, m:6, n:6
that was supposed to be:
//c:6, d:6, e:6, f:5, g:6, h:5, j:6, k:6, m:6, n:6
So what this shows really, is that incrementing when applied directly to a var is evaluated immediately. But, if assignment of value is being done using = the evaluation of the incrementing is done either before or after the assignment of value depending on whether the ++ is before or after the var being incremented.
So when you realize that, then the following makes perfect sense:
var a = 9;
var b = 0;
b = a; //b = 9
b = ++a; //b = 10, a = 10, a was incremented before b was assigned value
b = a++; //b = 10, a = 11, when b was evaluated, a was still worth 10, then a incremented after b was assigned value
b = a++; //b = 11, a = 12, a incremented after b assigned value
alert("a: "+a+"\nb: "+b); //a:12, b:11
b = a++; //b = 10, a = 11
b = a++; //b = 11, a = 12
I forgot to add those /*slaps himself with a trout*/
er thanks for all that code but I barely know increments, never mind looping.
It's not that bad as it seems to be. Honest. In fact, they make your life heaven combined with a pack of beer (with a bit of exaggeration) in the easiest way possible :)
Waiting the day when you'll ask about loops and switches :)
Waiting the day when you'll ask about loops and switches
