jquery.autosize.js

// Autosize 1.15.1 - jQuery plugin for textareas
// (c) 2012 Jack Moore - jacklmoore.com
// license: www.opensource.org/licenses/mit-license.php

(function ($) {
	var
	defaults = {
		className: 'autosizejs',
		append: "",
		callback: false
	},
	hidden = 'hidden',
	borderBox = 'border-box',
	lineHeight = 'lineHeight',

	// border:0 is unnecessary, but avoids a bug in FireFox on OSX (http://www.jacklmoore.com/autosize#comment-851)
	copy = '<textarea tabindex="-1" style="position:absolute; top:-9999px; left:-9999px; right:auto; bottom:auto; border:0; -moz-box-sizing:content-box; -webkit-box-sizing:content-box; box-sizing:content-box; word-wrap:break-word; height:0 !important; min-height:0 !important; overflow:hidden;"/>',
	
	// line-height is conditionally included because IE7/IE8/old Opera do not return the correct value.
	copyStyle = [
		'fontFamily',
		'fontSize',
		'fontWeight',
		'fontStyle',
		'letterSpacing',
		'textTransform',
		'wordSpacing',
		'textIndent'
	],
	oninput = 'oninput',
	onpropertychange = 'onpropertychange',
	
	// to keep track which textarea is being mirrored when adjust() is called.
	mirrored,

	// the mirror element, which is used to calculate what size the mirrored element should be.
	mirror = $(copy).data('autosize', true)[0];

	// test that line-height can be accurately copied.
	mirror.style.lineHeight = '99px';
	if ($(mirror).css(lineHeight) === '99px') {
		copyStyle.push(lineHeight);
	}
	mirror.style.lineHeight = '';

	$.fn.autosize = function (options) {
		options = $.extend({}, defaults, options || {});

		$(mirror).appendTo('body');

		return this.each(function () {
			var
			ta = this,
			$ta = $(ta),
			minHeight = $ta.height(),
			maxHeight = parseInt($ta.css('maxHeight'), 10),
			active,
			resize,
			boxOffset = 0,
			value = ta.value,
			callback = $.isFunction(options.callback);

			if ($ta.data('autosize')) {
				// exit if autosize has already been applied, or if the textarea is the mirror element.
				return;
			}

			if ($ta.css('box-sizing') === borderBox || $ta.css('-moz-box-sizing') === borderBox || $ta.css('-webkit-box-sizing') === borderBox){
				boxOffset = $ta.outerHeight() - $ta.height();
			}

			resize = $ta.css('resize') === 'none' ? 'none' : 'horizontal';

			$ta.css({
				overflow: hidden,
				overflowY: hidden,
				wordWrap: 'break-word',
				resize: resize
			}).data('autosize', true);

			// Opera returns '-1px' when max-height is set to 'none'.
			maxHeight = maxHeight && maxHeight > 0 ? maxHeight : 9e4;

			function initMirror() {
				mirrored = ta;
				mirror.className = options.className;

				// mirror is a duplicate textarea located off-screen that
				// is automatically updated to contain the same text as the
				// original textarea.  mirror always has a height of 0.
				// This gives a cross-browser supported way getting the actual
				// height of the text, through the scrollTop property.
				$.each(copyStyle, function(i, val){
					mirror.style[val] = $ta.css(val);
				});
			}

			// Using mainly bare JS in this function because it is going
			// to fire very often while typing, and needs to very efficient.
			function adjust() {
				var height, overflow, original;

				if (mirrored !== ta) {
					initMirror();
				}

				// the active flag keeps IE from tripping all over itself.  Otherwise
				// actions in the adjust function will cause IE to call adjust again.
				if (!active) {
					active = true;
					mirror.value = ta.value + options.append;
					mirror.style.overflowY = ta.style.overflowY;
					original = parseInt(ta.style.height,10);

					// Update the width in case the original textarea width has changed
					mirror.style.width = $ta.width() + 'px';

					// Needed for IE7 to reliably return the correct scrollHeight
					mirror.scrollTop = 0;

					// Set a very high value for scrollTop to be sure the
					// mirror is scrolled all the way to the bottom.
					mirror.scrollTop = 9e4;

					height = mirror.scrollTop;
					if (height > maxHeight) {
						height = maxHeight;
						overflow = 'scroll';
					} else if (height < minHeight) {
						height = minHeight;
					}
					height += boxOffset;
					ta.style.overflowY = overflow || hidden;

					if (original !== height) {
						ta.style.height = height + 'px';
						if (callback) {
							options.callback.call(ta);
						}
					}
					
					// This small timeout gives IE a chance to draw it's scrollbar
					// before adjust can be run again (prevents an infinite loop).
					setTimeout(function () {
						active = false;
					}, 1);
				}
			}

			if (onpropertychange in ta) {
				if (oninput in ta) {
					// Detects IE9.  IE9 does not fire onpropertychange or oninput for deletions,
					// so binding to onkeyup to catch most of those occassions.  There is no way that I
					// know of to detect something like 'cut' in IE9.
					ta[oninput] = ta.onkeyup = adjust;
				} else {
					// IE7 / IE8
					ta[onpropertychange] = adjust;
				}
			} else {
				// Modern Browsers
				ta[oninput] = adjust;

				// The textarea overflow is now hidden, but Chrome doesn't reflow the text to account for the
				// new space made available by removing the scrollbars. This workaround causes Chrome to reflow the text.
				ta.value = '';
				ta.value = value;
			}

			$(window).resize(adjust);

			// Allow for manual triggering if needed.
			$ta.bind('autosize', adjust);

			// Call adjust in case the textarea already contains text.
			adjust();
		});
	};
}(window.jQuery || window.Zepto));