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var Scroller = (function(){
var Scroller = {}
var prev, next
var webkitRatio = 1
Scroller.init = function(opt){
previous = opt.previous
next = opt.next
if (is_mobile) {
// document.body.addEventListener("touchstart", touchstart)
// document.body.addEventListener("touchmove", touchmove)
// document.body.addEventListener("touchend", touchend)
}
else {
document.body.addEventListener("wheel", wheelDelta)
document.body.addEventListener("keydown", keydown)
}
}
var touching = false, touchStartTime, touchStartY, touchEndY, touchDist, touchScrollTop
function touchstart (e) {
touching = true
touchStartTime = +(new Date)
touchStartY = touchEndY = e.touches ? e.touches[0].pageY : e.pageY
}
function touchmove (e) {
if (! touching) return
e.preventDefault()
var timestamp = +(new Date)
var duration = timestamp - touchStartTime
touchEndY = e.touches ? e.touches[0].pageY : e.pageY
touchDist = touchStartY - touchEndY
}
function touchend (e) {
if (! touching) return
e.preventDefault()
touching = false
var timestamp = +(new Date)
var duration = timestamp - touchStartTime
touchDist = touchStartY - touchEndY
if (Math.abs(touchDist) < 10 || duration < 100) {
step(1)
}
else {
touchDist > 0 ? step(1) : step(-1)
}
}
function wheelDelta (e){
e.preventDefault()
var deltaY = 0
// WebKit
if ( e.deltaY ) {
deltaY += e.deltaY * webkitRatio
}
else if ( e.wheelDeltaY ) {
deltaY += e.wheelDeltaY * webkitRatio
}
// Opera / Explorer 9
else if ( e.wheelDelta ) {
deltaY += e.wheelDelta * webkitRatio
}
// Firefox
else if ( e.detail ) {
deltaY -= e.detail * 2
}
wheel(deltaY)
}
var lastScrollEvent = +new Date(), lastDY = 0, lastSign = 0
function wheel (dy) {
if (isNaN(dy)) return
var now = +new Date(), newSign = sign(dy)
if ((now > lastScrollEvent + 300) ||
(lastSign !== newSign && Math.abs(dy) > Math.abs(lastDY*2)) ||
(lastSign === newSign && Math.log(Math.abs(dy)) > 1+Math.log(Math.abs(lastDY)))) {
step(sign(dy))
}
lastDY = dy
lastSign = newSign
lastScrollEvent = now
}
function step (n) {
var now = +new Date()
if (now < lastScrollEvent + 300) {
return
}
lastScrollEvent = now
if (n < 0) {
previous()
}
else {
next()
}
}
function keydown (e) {
// console.log(e.keyCode)
switch (e.keyCode) {
case 32: // space
e.preventDefault()
step(1)
break
case 36: // home
e.preventDefault()
break
case 35: // end
e.preventDefault()
break
case 33: // page up
case 38: // up
e.preventDefault()
step(-1)
break
case 34: // page down
case 40: // down
e.preventDefault()
step(1)
break
}
}
return Scroller
})()
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