jquery.elastic.source.js

/**
*	@name							Elastic
*	@descripton						Elastic is Jquery plugin that grow and shrink your textareas automaticliy
*	@version						1.6.3
*	@requires						Jquery 1.2.6+
*
*	@author							Jan Jarfalk
*	@author-email					jan.jarfalk@unwrongest.com
*	@author-website					http://www.unwrongest.com
*
*	@licens							MIT License - http://www.opensource.org/licenses/mit-license.php
*/

(function(jQuery){ 
	jQuery.fn.extend({  
		elastic: function() {
		
			//	We will create a div clone of the textarea
			//	by copying these attributes from the textarea to the div.
			var mimics = [
				'paddingTop',
				'paddingRight',
				'paddingBottom',
				'paddingLeft',
				'fontSize',
				'lineHeight',
				'fontFamily',
				'width',
				'fontWeight'];
			
			var pseudoUUID = function(p) {
				p = p || '';
				var u = function() { return(((1+Math.random())*0x10000)|0).toString(16).substring(1); }
				return(p+u()+u()+"-"+u()+"-"+u()+"-"+u()+"-"+u()+u()+u());
			};

			return this.each( function() {
				
				// Elastic only works on textareas
				if ( this.type != 'textarea' ) {
					return false;
				}
				
				var $textarea	=	jQuery(this),
					$twin		=	null,
					twinId		=	$textarea.data('elastic-twin');
					
				if ( twinId ) {
					$twin		=	jQuery('#'+twinId);
					update();
					return false;
				}
				
					
				var	lineHeight	=	parseInt($textarea.css('line-height'),10) || parseInt($textarea.css('font-size'),'10'),
					minheight	=	parseInt($textarea.css('height'),10) || lineHeight*3,
					maxheight	=	parseInt($textarea.css('max-height'),10) || Number.MAX_VALUE,
					goalheight	=	0,
					i 			=	0;
				
				twinId			=	pseudoUUID('elastic');
				$twin			=	jQuery('<div />').css({'position': 'absolute','display':'none','word-wrap':'break-word'});
				$twin.attr('id',twinId);
				$textarea.data('elastic-twin',twinId);
				
				// Opera returns max-height of -1 if not set
				if (maxheight < 0) { maxheight = Number.MAX_VALUE; }
					
				// Append the twin to the DOM
				// We are going to meassure the height of this, not the textarea.
				$twin.appendTo($textarea.parent());
				
				// Copy the essential styles (mimics) from the textarea to the twin
				var i = mimics.length;
				while(i--){
					$twin.css(mimics[i].toString(),$textarea.css(mimics[i].toString()));
				}
				
				
				// Sets a given height and overflow state on the textarea
				function setHeightAndOverflow(height, overflow){
					curratedHeight = Math.floor(parseInt(height,10));
					if($textarea.height() != curratedHeight){
						$textarea.css({'height': curratedHeight + 'px','overflow':overflow});
						
					}
				}
				
				
				// This function will update the height of the textarea if necessary 
				function update() {
					
					// Get curated content from the textarea.
					var textareaContent = $textarea.val().replace(/&/g,'&amp;').replace(/  /g, '&nbsp;').replace(/<|>/g, '&gt;').replace(/\n/g, '<br />');
					
					// Compare curated content with curated twin.
					var twinContent = $twin.html().replace(/<br>/ig,'<br />');
					
					if((textareaContent+'&nbsp;' != twinContent) || ($textarea.width() != $twin.width())){
					
						// Set twin to the same width as the textarea
						$twin.width($textarea.width());
						
						// Add an extra white space so new rows are added when you are at the end of a row.
						$twin.html(textareaContent+'&nbsp;');
						
						// Change textarea height if twin plus the height of one line differs more than 3 pixel from textarea height
						if(Math.abs($twin.height() + lineHeight - $textarea.height()) > 3){
							
							var goalheight = $twin.height()+lineHeight;
							if(goalheight >= maxheight) {
								setHeightAndOverflow(maxheight,'auto');
							} else if(goalheight <= minheight) {
								setHeightAndOverflow(minheight,'hidden');
							} else {
								setHeightAndOverflow(goalheight,'hidden');
							}
							
						}
						
					}
					
				}
				
				// Hide scrollbars
				$textarea.css({'overflow':'hidden'});
				
				// Update textarea size on keyup
				$textarea.keyup(function(){ update(); });
				
				// Define a custom event to allow manual updating
				$textarea.bind('elasticupdate', function(){ update(); });
				
				// And this line is to catch the browser paste event
				$textarea.live('input paste',function(e){ setTimeout( update, 250); });				
				
				// Run update once when elastic is initialized
				update();
				
			});
			
        } 
    }); 
})(jQuery);