why does counter not stop?

[bob]

Hi,

Question about For (...).
I did this:
for (i=1;i=5;i++)
alert(i)

and i get an infinite loop with value '5'. I thought that 'i=5' was the test
which must be 'true' in order to execute 'alert(i)'. It's normal that i
don't get 1 to 4 because in those case, the test is false. When i=5, i get
alert(i) with 5 but appearantely, i never equals 6.

By the way, is there a difference between i++ and ++i? I tried both but
didn't find any difference.

Thanks
bob

[David Dorward]

Re: why does counter not stop?

bob wrote:
[color=blue]
> Question about For (...).
> I did this:
> for (i=1;i=5;i++)
> alert(i)
>
> and i get an infinite loop with value '5'. I thought that 'i=5' was the
> test which must be 'true' in order to execute 'alert(i)'.[/color]

Two problems:

(1) The second parameter of the for loop has to be true to keep looping. It
will execute the content of block every time it loops.

(2) "=" is the assignment operator. The numerical test operator is "==".
[color=blue]
> It's normal that i don't get 1 to 4 because in those case[/color]

Nope. The first time round the loop you set i to 1, and then immediately
afterwards you set it to 5.
[color=blue]
>, the test is false.[/color]

i=5 is always true
[color=blue]
> When i=5, i get alert(i) with 5 but appearantely, i never equals 6.[/color]

Becuase you add one to it, and then set it back to 5 again.
[color=blue]
> By the way, is there a difference between i++ and ++i? I tried both but
> didn't find any difference.[/color]

It's a case of when the increment happens.

<script type="text/javascript">
i = 0;
document.write (i +'<br>'+ i++ +'<br>'+ i +'<br>'+ ++i +'<br>'+ i);
</script>

might make things clear if you follow it through carefully.

--
David Dorward http://dorward.me.uk/

[bob]

Re: why does counter not stop?

thanks for replying


"David Dorward" <dorward@yahoo. com> wrote in message
news:bhnf87$gm$ 1$8300dec7@news .demon.co.uk...[color=blue]
> bob wrote:
>[color=green]
> > Question about For (...).
> > I did this:
> > for (i=1;i=5;i++)
> > alert(i)
> >
> > and i get an infinite loop with value '5'. I thought that 'i=5' was the
> > test which must be 'true' in order to execute 'alert(i)'.[/color]
>
> Two problems:
>
> (1) The second parameter of the for loop has to be true to keep looping.[/color]
It[color=blue]
> will execute the content of block every time it loops.
>
> (2) "=" is the assignment operator. The numerical test operator is "==".
>[color=green]
> > It's normal that i don't get 1 to 4 because in those case[/color]
>
> Nope. The first time round the loop you set i to 1, and then immediately
> afterwards you set it to 5.
>[color=green]
> >, the test is false.[/color]
>
> i=5 is always true
>[color=green]
> > When i=5, i get alert(i) with 5 but appearantely, i never equals 6.[/color]
>
> Becuase you add one to it, and then set it back to 5 again.
>[color=green]
> > By the way, is there a difference between i++ and ++i? I tried both but
> > didn't find any difference.[/color]
>
> It's a case of when the increment happens.
>
> <script type="text/javascript">
> i = 0;
> document.write (i +'<br>'+ i++ +'<br>'+ i +'<br>'+ ++i +'<br>'+ i);
> </script>
>
> might make things clear if you follow it through carefully.
>
> --
> David Dorward http://dorward.me.uk/[/color]