Inserting VAL in :nth-child( X ) won't work

Why can't I use SlideNumber in the bottom...?? I tried to change var SlideNumber = 3; to SlideNumber = 3; but honestly, I'm fumbling in the dark.

if(window.location.hash != '') {
    var SlideNumber = 3;
    $('.slideshow').cycle({
        fx: 'blindY', // choose your transition type, ex: fade, scrollUp, shuffle, etc...
        speed:  700,
        cleartype:  1,
  开发者_开发百科      startingSlide: $(window.location.hash).index(),
        timeout: 3000,
          after: function(curr,next,opts) {             
            $("#menu ul li:nth-child(SlideNumber)").addClass("active");
            ready = true;
          } 

    });

Thank you in advance.

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To add, you can avoid concatenation and crank up the performance a bit by using the .eq filtering method (which takes a zero-based index):

$("#menu ul li").eq(slideNumber-1).addClass("active");

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To concatenate your SlideNumber variable into your selector, you need to break up your string and sandwich your variable between + operators:

$("#menu ul li:nth-child(" + SlideNumber + ")").addClass("active");

Otherwise your pseudo-class selector will simply appear as the string ":nth-child(SlideNumber)" which isn't quite what you intend.