(Javascript - Jquery) how to fadein LI elements randomly?

[hobier]

Hi ive got a set of li with hover effect, what i want is when the page loads ALL the li fadein randomly.

i don't want to shuffle them.....they should keep their ordering intact meaning 1,2,3,4,5.... just want to make them appear on the page randomly and stay there

test page: http://humayunrehman.com/hovertest/

[crashguy]

Not actual code but:

- Grab elements by classname or tagname put into array (classname is better if you have other li elements on page)

- create loop, loop until no items left in array

- get length of array

- get random number based on length of array

- fade in item based on random number

- remove item from array

- end loop

[hobier]

  On 14/06/2010 at 08:36, crashguy said:

Not actual code but:

- Grab elements by classname or tagname put into array (classname is better if you have other li elements on page)

- create loop, loop until no items left in array

- get length of array

- get random number based on length of array

- fade in item based on random number

- remove item from array

- end loop

not so advance with jquery, this is the ID name:

ul#blocks

tried

var randomnumber=Math.floor(Math.random()*$("#blocks").children().length

cant seem to get the number of li inside a ul

[hobier]

this is the effect i was hoping to incorporate:

http://boedesign.com/demos/jsquares/

[XakepaBG]

number of LI's inside this UL

var count = $('ul#blocks li').length;

targeting a single LI inside the UL

var $theLi = $('ul#blocks li:eq(2)'); //gets the THIRD LI (children array is 0-based)

it'd be wise to play with the basics of using jQuery (selectors, attributes, traversing, manipulation) before you dive in the deep water and try animations and effects in collections of elements...

[Calculator]

I think I found a neat solution for this problem. We can use the fact that jQuery collections can behave just like native arrays, and thus we can also shuffle them like we would shuffle arrays.

I found a great shuffling algorithm on http://jsfromhell.com/array/shuffle, which I use for this solution. The only thing I changed is the way Math.random() * i gets rounded. In the original code, the author uses parseInt() to round the number down, but this is much slower than using Math.floor(). I wanted to change it to Math.floor(), until I found an even faster way to do this using bitwise operators. Simply put, (n | 0) or (n >> 0) is the fastest way to round a positive floating point number to the greatest integer smaller than the float.

With this shuffle function, I first tried to get an array out of the jQuery collection, shuffle it and make a jQuery collection out of it again. However, due to the way the shuffle function works, I can simply throw the jQuery collection straight into it, shuffling the order of the jQuery collection - simple as that!

Finally, to make the next item in the list fade in after the previous animation is done, I use a helper function. This helper takes a list of items, animates the first item in the list and calls itself in the animation callback after popping the first item from its list. The result is a perfect animation of items nicely waiting for each other to fade in.

So there you have it, a solution which shows some of the lesser known beauties of JavaScript and jQuery. Sure, this is pretty advanced stuff and it may look all very complex at first, but try to study what's happening and soon you'll see the beauty of it. :)

(function($) {
	// Get the list items and hide them
	var items = $("#blocks > li").css({opacity:0});
	// Shuffle them
	shuffle(items);
	// Start the fade-in queue
	nextItemFade(items);

	// Animation callback to start next fade-in
	function nextItemFade(items) {
		// Fade in the first element in the collection
		items.eq(0).animate({opacity:1}, 500, function() {
			// Recurse, but without the first element
			nextItemFade(items.slice(1));
		});
	}

	// Shuffles an array
	// Based on http://jsfromhell.com/array/shuffle
	function shuffle(a) {
		var j,              // Random position
		    x,              // Last item
		    i = a.length;   // Iterator
		// Loop through the array
		while(i) {
			// Select a random position
			j = (Math.random() * i) | 0;
			// Get the last item in the array
			x = a[--i];
			// Swap the last item with the item at the selected position
			a[i] = a[j];
			a[j] = x;
		}
		return a;
	}

	/* Minified version
	function shuffle(a) {
		for(var j, x, i = a.length; i; j = (Math.random() * i) | 0, x = a[--i], a[i] = a[j], a[j] = x);
		return a;
	} */
})(jQuery);

[hobier]

wow....amazin stuff...thanks a lot.

im a graphic design whos trying to step into the realms of web development and its fascinating to see what one can achieve without the use of flash....

jquery is great.....i'm trying to see through your code.....

now all is left is to try to figure out how to trigger the hover event AFTER all the li have faded In.......currently, while the li are fading in randomly if a user hovers on any of the li the hover event is triggered and everything just stops right there.....

big big thanks to you....

[hobier]

doesn't seem to work in IE8 no random fades nor the hover event works properlu...and in IE 7 random fade works but hover event has the same problem (hover span not showing)....argghhhhhh

[mokes]

Sorry to bring this topic back from the dead, but is it possible to make that function loop through the array indefinitely, instead of just running through all of the elements once?