Variable in jQuery selector

Question

Hopefully this is a quick easy one for you.

Here is my code:

var p7slide = 0;
$("#p7-forward").click (function () {
    p7animate = null;
    if (p7slide == 6)   {
        $("#p7-6").fadeOut("slow", function ()  {
            p7slide = 0;            
        });
    }
    else    {
        p7slide++;
        $("#p7-" + p7slide).fadeIn("slow");
        <!--$("#p7-" + "p7slide - 1").fadeOut("slow");-->
    };
});

The part i refer to is the commented out line in the else statement.

What i need this to do is to find p7slide and take 1 from this value. Then use that as the selector. E.g. If p7slide = 2 the selector would put together #p7-1. For some reason this statement isn't working.

Any ideas what Ive done wrong here?

Thanks

Note that HTML comments are invalid in JavaScript.

Felix Kling
– Felix Kling

2011-12-14 12:18:03 +00:00
Commented Dec 14, 2011 at 12:18 — Felix Kling
– Felix Kling, Commented Dec 14, 2011 at 12:18

StuperUser · Accepted Answer · 2011-12-14 12:22:18Z

2

You've hard coded it as a string rather than an operation.

replace

$("#p7-" + "p7slide - 1").fadeOut("slow");

with

var slideNumber = p7slide - 1;
$("#p7-" + slideNumber).fadeOut("slow");

Note: In JS, if you use + operator with a string first, then a number, then you'll concatenate the number as a string to the end of the first string, see: http://www.quirksmode.org/js/strings.html for more details.

edited Dec 14, 2011 at 12:22

answered Dec 14, 2011 at 12:17

StuperUser

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Comments

Dominic Green · Accepted Answer · 2011-12-14 12:18:34Z

0

Try removing the " " tags as you cannot use numeric functions on a string

 $("#p7-" + p7slide - 1).fadeOut("slow");

answered Dec 14, 2011 at 12:18

Dominic Green

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1 Comment

StuperUser Over a year ago

"you cannot use numeric functions on a string" isn't accurate. + isn't a function, it's an operator. You can use operator with string, but if the first operand is a string, it will concatenate then number as a string to the first, see: quirksmode.org/js/strings.html for more details.

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