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Thread: JavaScript newbie: - - decrement problem

  1. #1
    Join Date
    Mar 2008

    JavaScript newbie: - - decrement problem

    Hi everyone,

    I'm new to JS,and am having a little trouble with my script. It's a picture slide show.

    Basically, when I click 'Previous' to call the 'moveToPreviousSlide' function, on the first call, it increments instead of decrements.

    Say I'm currently viewing image 3, when I then click 'previous', it keeps going to image 4 instead, and then goes back down to 3, and then 2, instead of going straight to 2.

    Here is what I've made so far:

    <script type="text/javascript">
    	var index = 0;
    	var titles = [1,2,3,4,5,6];
    	function moveToNextSlide()
    			if(index > 5)
    					index = 0;
    			var slideName = "images/slideshow/template" + titles[index++] + ".jpg";
    			var img1 = document.getElementById("img1");
    			img1.src = slideName;
    	function moveToPreviousSlide()//on first call still increments by 1
    			var slideName = "images/slideshow/template" + titles[index--] + ".jpg";
    			var img1 = document.getElementById("img1");
    			img1.src = slideName;
    If anyone can tell me how to correct this I'd be very grateful!!

    Many thanks!

    Last edited by Swerve; December 1st, 2008 at 12:09 PM.

  2. #2
    Join Date
    Apr 2005

    Re: JavaScript newbie: - - decrement problem

    You're using the post-increment/decrement operator while you probably want to use the pre-increment/decrement operator.

    - petter

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