# Javascript test %4

Discussion in 'Javascript' started by Cogito, Mar 7, 2007.

1. ### CogitoGuest

I'm trying to understand some Javascript code from a certain site.
Could you please tell me what does this test mean?
if ( j%4 == 0 )
What does %4 test for and is there a web site that explains it and,
presumably, also %1, %2 etc.

Cogito, Mar 7, 2007

3. ### Randy WebbGuest

Cogito said the following on 3/6/2007 11:52 PM:
> I'm trying to understand some Javascript code from a certain site.
> Could you please tell me what does this test mean?
> if ( j%4 == 0 )
> What does %4 test for and is there a web site that explains it and,
> presumably, also %1, %2 etc.

The statement above means if the remainder of dividing j by 4 is 0.
You can change the 0 to anything smaller than j.

--
Randy
Chance Favors The Prepared Mind
comp.lang.javascript FAQ - http://jibbering.com/faq/index.html
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/

Randy Webb, Mar 7, 2007
4. ### CogitoGuest

Such quick replies. It's simply magic.
Thank you guys.

Cogito, Mar 7, 2007
5. ### Evertjan.Guest

Randy Webb wrote on 07 mrt 2007 in comp.lang.javascript:

> Cogito said the following on 3/6/2007 11:52 PM:
>> I'm trying to understand some Javascript code from a certain site.
>> Could you please tell me what does this test mean?
>> if ( j%4 == 0 )
>> What does %4 test for and is there a web site that explains it and,
>> presumably, also %1, %2 etc.

>
> The statement above means if the remainder of dividing j by 4 is 0.
> You can change the 0 to anything smaller than j.
>

There is no such limitation.

;-)

But to be useful:
Anything? Also any fraction or any negative integer?

--
Evertjan.
The Netherlands.

Evertjan., Mar 7, 2007
6. ### Dr J R StocktonGuest

In comp.lang.javascript message <Xns98EC70FE9A9DBeejj99@194.109.133.242>
, Wed, 7 Mar 2007 10:06:28, Evertjan. <>
posted:
>Randy Webb wrote on 07 mrt 2007 in comp.lang.javascript:
>
>> Cogito said the following on 3/6/2007 11:52 PM:
>>> I'm trying to understand some Javascript code from a certain site.
>>> Could you please tell me what does this test mean?
>>> if ( j%4 == 0 )
>>> What does %4 test for and is there a web site that explains it and,
>>> presumably, also %1, %2 etc.

>>
>> The statement above means if the remainder of dividing j by 4 is 0.
>> You can change the 0 to anything smaller than j.
>>

>
>There is no such limitation.
>
>;-)
>
>But to be useful:
>Anything? Also any fraction or any negative integer?

Yes, yes.

ISTM that, unless the code is an obfuscation of false, the right hand
side must be, or have a chance of being, smaller in absolute value than
the divisor is or may be. And, generally, all three values need to be
such as can be represented exactly by an IEEE Double, including NaN, if
the statement is to be reliably usable.

The OP could easily have answered his question by searching the PDF of
the Standards (FAQ cites one of them, IIRC) for "%".

The sections of the standards dealing with the % operator need
rewriting; at present, they use "floating-point" to mean "non-integer".
All Numbers are floating point currently.

It's a good idea to read the newsgroup and its FAQ. See below.

--
(c) John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v6.05 IE 6
news:comp.lang.javascript FAQ <URL:http://www.jibbering.com/faq/index.html>.
<URL:http://www.merlyn.demon.co.uk/js-index.htm> jscr maths, dates, sources.

Dr J R Stockton, Mar 7, 2007
7. ### Randy WebbGuest

Evertjan. said the following on 3/7/2007 5:06 AM:
> Randy Webb wrote on 07 mrt 2007 in comp.lang.javascript:
>
>> Cogito said the following on 3/6/2007 11:52 PM:
>>> I'm trying to understand some Javascript code from a certain site.
>>> Could you please tell me what does this test mean?
>>> if ( j%4 == 0 )
>>> What does %4 test for and is there a web site that explains it and,
>>> presumably, also %1, %2 etc.

>> The statement above means if the remainder of dividing j by 4 is 0.
>> You can change the 0 to anything smaller than j.
>>

>
> There is no such limitation.
>
> ;-)

Tis true, but the results are pretty useles if k is smaller than j in j%k.

> But to be useful:
> Anything? Also any fraction or any negative integer?

Yes. Or at least testing doesn't throw up on fractions or negative
integers.

--
Randy
Chance Favors The Prepared Mind
comp.lang.javascript FAQ - http://jibbering.com/faq/index.html
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/

Randy Webb, Mar 7, 2007
8. ### Dr J R StocktonGuest

In comp.lang.javascript message <>,
Wed, 7 Mar 2007 08:51:12, Randy Webb <> posted:
>Evertjan. said the following on 3/7/2007 5:06 AM:
>> Randy Webb wrote on 07 mrt 2007 in comp.lang.javascript:
>>
>>> Cogito said the following on 3/6/2007 11:52 PM:
>>>> I'm trying to understand some Javascript code from a certain site.
>>>> Could you please tell me what does this test mean?
>>>> if ( j%4 == 0 )
>>>> What does %4 test for and is there a web site that explains it and,
>>>> presumably, also %1, %2 etc.
>>> The statement above means if the remainder of dividing j by 4 is 0.
>>> You can change the 0 to anything smaller than j.
>>>

>> There is no such limitation.
>> ;-)

>
>Tis true, but the results are pretty useles if k is smaller than j in j%k.

That is certainly not true, and neither is the converse. But if j is
*always* smaller than k, the operation is pointless.

>> But to be useful: Anything? Also any fraction or any negative
>>integer?

>
>Yes. Or at least testing doesn't throw up on fractions or negative
>integers.

Testing has its uses; but the standards are sufficiently clear. For
example, -6.875%1.25 has a meaning, and the operation gives it.

--
(c) John Stockton, Surrey, UK. ???@merlyn.demon.co.uk Turnpike v6.05 MIME.
Web <URL:http://www.merlyn.demon.co.uk/> - FAQish topics, acronyms, & links.
In MS OE, choose Tools, Options, Send; select Plain Text for News and E-mail.
Don't quote more than is needed, and respond after each quoted part.

Dr J R Stockton, Mar 7, 2007
9. ### Randy WebbGuest

Dr J R Stockton said the following on 3/7/2007 11:48 AM:
> In comp.lang.javascript message <>,
> Wed, 7 Mar 2007 08:51:12, Randy Webb <> posted:
>> Evertjan. said the following on 3/7/2007 5:06 AM:
>>> Randy Webb wrote on 07 mrt 2007 in comp.lang.javascript:

<snip>

>>> But to be useful: Anything? Also any fraction or any negative
>>> integer?

>> Yes. Or at least testing doesn't throw up on fractions or negative
>> integers.

>
> Testing has its uses; but the standards are sufficiently clear. For
> example, -6.875%1.25 has a meaning, and the operation gives it.

Yeah, the "standards" are sufficiently useless also. We all know how
abundantly clear the "standards" are with regards to toFixed() now don't we?

Keep the "standards", give me testing.

--
Randy
Chance Favors The Prepared Mind
comp.lang.javascript FAQ - http://jibbering.com/faq/index.html
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/

Randy Webb, Mar 8, 2007