For loop problem

JavaScript
1

I’m not good with JavaScript so please, if there is a simple solution/explanation, I would appreciate it.

Now on to my problem…

I’ve been using a for loop to speed up repetitive tasks and it seems to work great, till now.


<script type="text/javascript">

var count=0;

for (count=0;count<30;count+=2.4) //2.4 doesn't work consistently//
	{
		document.write(count+"<br />");
	}

</script>

The results I get start out correct then go wrong.

FireFox (3.6.16)____________________Results with IE 8____________________Results with Opera
0________________________________0________________________________0
2.4______________________________2.4_______________________________2.4
4.8______________________________4.8_______________________________4.8
7.199999999999999________________7.199999999999999_________________7.2
9.6______________________________9.6_______________________________9.6
12______________________________12________________________________12
14.4____________________________14.4_______________________________14.4
16.8____________________________16.8_______________________________16.8
19.2____________________________19.2_______________________________19.2
21.599999999999998______________21.599999999999998_________________21.60
23.999999999999996______________23.999999999999996_________________23.999999999999996
26.399999999999995______________26.399999999999995_________________26.399999999999995
28.799999999999994______________28.799999999999993_________________28.799999999999994

If I use…

<script type="text/javascript">

var count=0;

for (count=0;count<30;count+=1) //1, 2, 3, etc.. works fine//
	{
		document.write(count+"<br />");
	}

</script>

OR

<script type="text/javascript">

var count=0;

for (count=0;count<30;count+=1.5) //1.5 works fine//
	{
		document.write(count+"<br />");
	}

</script>

It counts like it should.

So why is it when I use “2.4” it doesn’t count properly?
And why does it produce different results in different browsers?

2

You could use this hacky addition to sort the rounding out:

for (count=0;count<30;count+=2.4)
    {
        document.write(Math.round(count*10)/10+"<br />");
    }
3

That worked for me. Thank You.

It still doesn’t make sense why it doesn’t work without the fix and why different browsers give different results.

Again, thank you.

EDIT:

Another suggestion I got was to use…

for (count=0;count<30;count+=2.4)
{
document.write(count.toFixed(1)+"<br />");
}

Which works as well, just has a permanent float which is not a problem (for this project).

4

You’re right, it doesn’t make sense.

Here’s an article that can help to explain why.
Why I Love ECMAScript 4: Real Decimals

5

Thanks for the help. Still kinda Greek to me, but it helped.

6

Nice link. Will be interesting to see if the rounding or 1DP solutions above remain quicker than the proposed decimal types.