JS animate to auto function

gistfile1.js

jQuery.fn.animateHeightAuto = function(speed, callback) {

	var height;

	return this.each(function(i, $element) {

		var $this = $( $element );
		var heightBackup = $this.css('height');

		$this.css({
			'height': 'auto'
		});

		height = $this.css('height');

		$this.css({
			'height': heightBackup,
		});

		$this.animate({
			'height': height,
		}, speed, callback);

	});
}