https://shikinoyakata-nasu.com/common/js/vendor/form/jquery.easing.js

1/*
2 * jQuery Easing v1.3 - http://gsgd.co.uk/sandbox/jquery/easing/
3 *
4 * Uses the built in easing capabilities added In jQuery 1.1
5 * to offer multiple easing options
6 *
7 * TERMS OF USE - jQuery Easing
8 * 
9 * Open source under the BSD License. 
10 * 
11 * Copyright  2008 George McGinley Smith
12 * All rights reserved.
13 * 
14 * Redistribution and use in source and binary forms, with or without modification, 
15 * are permitted provided that the following conditions are met:
16 * 
17 * Redistributions of source code must retain the above copyright notice, this list of 
18 * conditions and the following disclaimer.
19 * Redistributions in binary form must reproduce the above copyright notice, this list 
20 * of conditions and the following disclaimer in the documentation and/or other materials 
21 * provided with the distribution.
22 * 
23 * Neither the name of the author nor the names of contributors may be used to endorse 
24 * or promote products derived from this software without specific prior written permission.
25 * 
26 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY 
27 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
28 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
29 *  COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
30 *  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
31 *  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 
32 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
33 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
34 * OF THE POSSIBILITY OF SUCH DAMAGE. 
35 *
36*/
37
38// t: current time, b: begInnIng value, c: change In value, d: duration
39jQuery.easing['jswing'] = jQuery.easing['swing'];
40
41jQuery.extend( jQuery.easing,
42{
43	easeInOutCirc: function (x, t, b, c, d) {
44		if ((t/=d/2) < 1) return -c/2 * (Math.sqrt(1 - t*t) - 1) + b;
45		return c/2 * (Math.sqrt(1 - (t-=2)*t) + 1) + b;
46	}
47});