jquery.elastic.source.js

/**
 *	@name							Elastic
 *	@descripton						Elastic is jQuery plugin that grow and shrink your textareas automatically
 *	@version						1.6.11
 *	@requires						jQuery 1.2.6+
 *
 *	@author							Jan Jarfalk
 *	@author-email					jan.jarfalk@unwrongest.com
 *	@author-website					http://www.unwrongest.com
 *
 *	@licence						MIT License - http://www.opensource.org/licenses/mit-license.php
 */

(function($){
	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',
				'border-top-width',
				'border-right-width',
				'border-bottom-width',
				'border-left-width',
				'borderTopStyle',
				'borderTopColor',
				'borderRightStyle',
				'borderRightColor',
				'borderBottomStyle',
				'borderBottomColor',
				'borderLeftStyle',
				'borderLeftColor'
			];

			return this.each( function() {

				// Elastic only works on textareas
				if ( this.type !== 'textarea' ) {
					return false;
				}

				var $textarea	= jQuery(this),
					$twin		= jQuery('<div />').css({
						'position'		: 'absolute',
						'display'		: 'none',
						'word-wrap'		: 'break-word',
						'white-space'	:'pre-wrap'
					}),
					lineHeight	= parseInt($textarea.css('line-height'),10) || parseInt($textarea.css('font-size'),'10'),
					minheight	= (parseInt($textarea.css('height'),10) || lineHeight*3-5),
					maxheight	= parseInt($textarea.css('max-height'),10) || Number.MAX_VALUE,
					goalheight	= 0;

				// 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()));
				}

				// Updates the width of the twin. (solution for textareas with widths in percent)
				function setTwinWidth(){
					var curatedWidth = Math.floor(parseInt($textarea.width(),10));
					if($twin.width() !== curatedWidth){
						$twin.css({'width': curatedWidth + 'px'});

						// Update height of textarea
						update(true);
					}
				}

				// Sets a given height and overflow state on the textarea
				function setHeightAndOverflow(height, overflow){

					var curratedHeight = Math.floor(parseInt(height,10));
					if($textarea.height() !== curratedHeight && $textarea.val() != ''){
						$textarea.css({'height': curratedHeight + 'px','overflow':overflow});
					}
				}

				// This function will update the height of the textarea if necessary
				function update(forced) {

					// Get curated content from the textarea.
					var textareaContent = $textarea.val().replace(/&/g,'&amp;').replace(/ {2}/g, '&nbsp;').replace(/<|>/g, '&gt;').replace(/\n/g, '<br />');

					// Compare curated content with curated twin.
					var twinContent = $twin.html().replace(/<br>/ig,'<br />');

					if(forced || textareaContent+'&nbsp;' !== twinContent){

						// 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, change, cut and paste
				$textarea.bind('keyup change cut paste', function(){
					update();
				});

				// Update width of twin if browser or textarea is resized (solution for textareas with widths in percent)
				jQuery(window).bind('resize', setTwinWidth);
				$textarea.bind('resize', setTwinWidth);
				$textarea.bind('update', update);

				// Compact textarea on blur
				$textarea.bind('blur',function(){
					if($twin.height() < maxheight){
						if($twin.height() > minheight) {
							$textarea.height($twin.height() + 22);
						} else {
							$textarea.height(minheight);
						}
					}
				});

				// And this line is to catch the browser paste event
				$textarea.bind('input paste',function(e){ setTimeout( update, 250); });

				// Run update once when elastic is initialized
				update();

			});

		}
	});
})(jQuery);