Auto-growing textareas with jQuery — The perfectionist way

autogrow.jquery.js

/* jQuery version of Autogrow script from
   Mobile HTML5 Boilerplate - http://bit.ly/l4j1RZ
   Adapted by Iraê http://bit.ly/kBfnaD */

$(document).delegate('textarea', 'keyup', function(event) {
	var self = $(this),
		textLineHeight = self.data('textLineHeight'),
		currentHeight = self.data('currentHeight'),
		newHeight = this.scrollHeight;

	if(!textLineHeight) { // init this particular textarea
		textLineHeight = parseInt(self.css('line-height'),10);
		currentHeight = self.height();
		self.css('overflow','hidden')
	}

	if (newHeight > currentHeight) {
		newHeight = newHeight + 3 * textLineHeight;
		self.height(newHeight);
		self.data('currentHeight',newHeight)
	}
});

LICENSE

MIT License
===========

Copyright (c) 2009–2011
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.


BSD License
===========

Copyright (c) 2011
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
  * Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.
  * Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.
  * Neither the name of the Organization nor the
    names of its contributors may be used to endorse or promote products
    derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

I wrote a post explaining some of the advantages of this gist compared to what I could find in the internet to do the same thing. Here it is: http://bit.ly/kBfnaD

Add some CSS magic if you want ;)

textarea {
   -webkit-transition: height 300ms ease-out;
      -moz-transition: height 300ms ease-out;
        -o-transition: height 300ms ease-out;
           transition: height 300ms ease-out;
}