jquery.mobile.alphascroll.js

( function( $ ) {

	$.fn.extend({

		alphascroll: function() {

			return this.each( function() {

				var content  = $( this ),
					alphabet = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'],
					shortAlphabet = ['a','d','g','j','m','p','s','w','z'],
					dividers = [],
					dividerClass,
					scrollbar = '';

				// attach classes to list autodividers
				$( content ).find( '.ui-li-divider' ).each( function() {
					dividerClass = $( this ).html().toLowerCase();
					dividers.push( dividerClass );
					$( this ).addClass( dividerClass );
				});

				// create and display the scrollbar
				function createScrollbar() {
					// generate scrollbar HTML
					$( alphabet ).each( function( index, value ) {
						// attach the alphascroll-item class to each letter if there is a corresponding divider (acts as a link)
						if ( $.inArray( value, dividers ) > -1 ) {
							scrollbar += '<li id="alphascroll-' + value + '" class="alphascroll-item" unselectable="on">' + value.toUpperCase() + '</li>';
						}
						else {
							scrollbar += '<li id="alphascroll-' + value + '" unselectable="on">' + value.toUpperCase() + '</li>';
						}
					});

					// attach scrollbar to page
					$( content ).wrap( '<div />' );
					var wrapper = $( content ).parent();
					$( wrapper ).prepend( '<ul class="alphascroll">' + scrollbar + '</ul>' );
					var alphascroll = $( content ).closest( 'div' ).children( '.alphascroll' );

					// bind touch event to scrollbar (for touch devices)
					$( alphascroll ).bind( 'touchmove', function( event ) {
						event.preventDefault();
						var touch = event.originalEvent.touches[0] || event.originalEvent.changedTouches[0];
						// scroll to divider position
						alphaScroll( touch.pageY );
					});

					// bind mouse events to scrollbar (for desktop browsers)
					$( alphascroll ).bind( 'mousedown', function() {
						$( '.ui-page-active' ).bind( 'mousemove', function( event ) {
							// prevent text selection while scrolling
							$( this ).css({
								"-webkit-user-select" : "none",
								"-moz-user-select"    : "none",
								"-ms-user-select"     : "none",
								"user-select"         : "none"
							});
							// scroll to divider position
							alphaScroll( event.pageY );
						});

						// return page to normal functioning after mouseup
						$( '.ui-page-active' ).bind( 'mouseup', function() {
							// release mousemove event control
							$( '.ui-page-active' ).unbind( 'mousemove' );
							// return text selection to default
							$( this ).css({
								"-webkit-user-select" : "text",
								"-moz-user-select"    : "text",
								"-ms-user-select"     : "text",
								"user-select"         : "text"
							});
						});
					});

					// use short scrollbar if screen is short (like landscape on an iPhone)
					if ( $( window ).height() <= 320  ) {
						truncateScrollbar();
					}
				}

				// handle orientation changes
				$( window ).bind( 'orientationchange', function() {
					$( '.alphascroll' ).unwrap().remove();
					scrollbar = '';
					createScrollbar();
				});

				function truncateScrollbar() {
					$( '.alphascroll li' ).each( function( index, value ) {
						if ( $.inArray( $( this ).html().toLowerCase(), shortAlphabet ) < 0 ) {
							$( this ).html( '&#183;' ).addClass( 'truncated' );
						}
					});
				}

				// do the scroll
				function alphaScroll( y ) {
					$( '.alphascroll-item' ).each( function() {
						if ( ! ( y <= $( this ).offset().top || y >= $( this ).offset().top + $( this ).outerHeight() ) ) {
							var scroll_id = $( this ).attr( 'id' ),
								letter    = scroll_id.split( '-' ),
								target    = $( '.' + letter[1] ),
								position  = target.position(),
								header_height;

							// offset scroll-top if header is displayed
							if ( $( '.ui-page-active [data-role="header"]' ).hasClass( 'ui-fixed-hidden' ) ) {
								header_height = 0;
							}
							else {
								header_height = $( '.ui-page-active [data-role="header"]' ).height();
							}

							// scroll the page
							$.mobile.silentScroll( position.top - header_height );
						}
					});
				}

				// generate scrollbar on invokation
				createScrollbar();
			});
		}
	});

})( jQuery );