https://www.ast-lab.jp/js/tinyscrolling.js

1/* Tiny Scrolling - a smooth navigation between internal links and their destinations
2by Marco Rosella - http://www.centralscrutinizer.it/en/design/js-php/tiny-scrolling
3based on the works by Travis Beckham and Brian McAllister.
4                v0.3 - March 27, 2006
5*/
6window.onload = function() {
7	tinyScrolling.init();
8	}
9
10var tinyScrolling = {
11	speed : 30,      //set here the scroll speed: when this value increase, the speed decrease. 
12	maxStep: 80,	 //set here the "uniform motion" step for long distances
13	brakeK: 3,		 //set here the coefficient of slowing down
14	hash:null,		
15	currentBlock:null,
16	requestedY:0,
17	init: function() {
18			var lnks = document.getElementsByTagName('a');   
19			for(var i = 0, lnk; lnk = lnks[i]; i++) {   
20				if ((lnk.href && lnk.href.indexOf('#') != -1) &&  ( (lnk.pathname == location.pathname) ||
21				('/'+lnk.pathname == location.pathname) ) && (lnk.search == location.search)) {  
22				lnk.onclick = tinyScrolling.initScroll;   		
23				}   
24			}
25	},
26	getElementYpos: function(el){
27			var y = 0;
28			while(el.offsetParent){  
29				y += el.offsetTop    
30				el = el.offsetParent;
31			}	return y;
32	},		
33	getScrollTop: function(){
34			if(document.all) return (document.documentElement.scrollTop) ? document.documentElement.scrollTop : document.body.scrollTop;
35			else return window.pageYOffset;   
36	},	
37	getWindowHeight: function(){
38			if (window.innerHeight)	return window.innerHeight;
39			if(document.documentElement && document.documentElement.clientHeight) return document.documentElement.clientHeight;
40	},
41	getDocumentHeight: function(){
42			if (document.height) return document.height;
43			if(document.body.offsetHeight) return document.body.offsetHeight;
44	},
45	initScroll: function(e){
46			var targ;  
47			if (!e) var e = window.event;
48			if (e.target) targ = e.target;
49			else if (e.srcElement) targ = e.srcElement;
50			
51			//ƒCƒ[ƒWƒZƒbƒg‚̑Ώˆ
52			do
53			{
54				if (typeof(targ.tagName) != "undefined")
55				{
56					//ƒŠƒ“ƒN‚Å‚È‚©‚Á‚½ê‡‚̑Ώˆ
57					if (targ.tagName.toLowerCase() == "a")
58					{
59						break;
60					}
61				}
62				targ = targ.parentNode;
63			} while(targ != null)
64			
65			if (targ == null)
66			{
67				return ;
68			}
69			
70			tinyScrolling.hash = targ.href.substr(targ.href.indexOf('#')+1,targ.href.length); 
71			tinyScrolling.currentBlock = document.getElementById(tinyScrolling.hash);   
72			if(!tinyScrolling.currentBlock) return;
73			tinyScrolling.requestedY = tinyScrolling.getElementYpos(tinyScrolling.currentBlock); 
74			tinyScrolling.scroll();  
75			return false;
76	},
77	scroll: function(){
78			var top  = tinyScrolling.getScrollTop();
79			if(tinyScrolling.requestedY > top) {  
80				var endDistance = Math.round((tinyScrolling.getDocumentHeight() - (top + tinyScrolling.getWindowHeight())) / tinyScrolling.brakeK);
81				endDistance = Math.max(Math.round((tinyScrolling.requestedY-top)/ tinyScrolling.brakeK), endDistance);
82				var offset = Math.max(2, Math.min(endDistance, tinyScrolling.maxStep));
83			} else { var offset = - Math.min(Math.abs(Math.round((tinyScrolling.requestedY-top)/ tinyScrolling.brakeK)), tinyScrolling.maxStep);
84			} window.scrollTo(0, top + offset);  
85			if(Math.abs(top-tinyScrolling.requestedY) <= 1 || tinyScrolling.getScrollTop() == top) {
86				window.scrollTo(0, tinyScrolling.requestedY);
87				if(!document.all || window.opera) location.hash = tinyScrolling.hash;
88				tinyScrolling.hash = null;
89			} else 	setTimeout(tinyScrolling.scroll,tinyScrolling.speed);
90	}		
91}