how to preform subtraction on a string
Aside from inserting illegal attributes into an tag and invalidating my HTML, I've never done what I am trying to do before and will most likely benefit from this answer in other areas of my work.
开发者_如何学CI think the problem is I am trying to subtract "1" from a string "$(this).attr('num')"
This might work if I first convert "$(this).attr('num')" into an integer and then subtract "1" from it.
I am open to any other solutions. Thanks
//
$("#jumpPreviousButton").click(function(){
var imageNumber = $(this).attr('num');
$("#bgImageBox").css({
"background-image": "url(/galleryImages/worksImage"
+ imageNumber - 1
+".jpg)"
}).attr('num', imageNumber - 1);
return false;}
);
//
As you say, converting it to integer first will help. Use the parseInt() function for that. :) (Or parseFloat() if it is a floating point number.)
use parseInt but don't use parseInt without a radix
The parseInt() function parses a string and returns an integer.
The signature is parseInt(string, radix)
so the answer to your question is:
var imageNumber = parseInt($(this).attr('num'), 10);
The second argument forces parseInt to use a base ten numbering system.
- The default input type for ParseInt() is decimal (base 10).
- If the number begins in "0", it is assumed to be octal (base 8).
- If it begins in "0x", it is assumed to be hexadecimal
why? if $(this).attr('num') would be "08" parsInt without a radix would become 0
Why dont you use jquery's data() function instead of attr() to add the num field to your tag.
- Jquery's data will not invalidate your markup
- You can add any data type in data, so there is no need to use
parseInt
For example: HTML:
<html>
<body>
<p>hello</p>
</body>
</html>
JS:
$('p').data('foo',52);
var val = $('p').data('foo');
alert(val);
$('p').data('foo', val + 1);
alert($('p').data('foo'));
This will alert 52 and then 53. You can see a demo here.
(parseInt(imageNumber) - 1)
if the number is an integer.
parseInt() function is your friend ;)
var imageNumber = parseInt($(this).attr('num'));
加载中,请稍侯......
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