var cityWrapper = document.querySelector('.city-wrapper-hook'); 
var cityScroller = document.querySelector('.scroller-hook'); 
var cities = document.querySelector('.cities-hook'); 
var shortcut = document.querySelector('.shortcut-hook'); 
var scroll; 
var shortcutList = []; 
var anchorMap = {};

function initCities() { 
 var y = 0; 
 var titleHeight = 28; 
 var itemHeight = 44; 
 var lists = ''; 
 var en = '
'; 
 cityData.forEach(function (group) { 
 var name = group.name; 
 lists += '
'+name+'
'; 
 lists += '
'; 
 group.cities.forEach(function(g) { 
 lists += '
'+ g.name +'
'; 
 }); 
 lists += '
'; 
 var name = group.name.substr(0, 1); 
 en += '
'+name+'
'; 
 var len = group.cities.length; 
 anchorMap[name] = y; 
 y -= titleHeight + len * itemHeight; 
 }); 
 en += '
'; 
 cities.innerHTML = lists; 
 shortcut.innerHTML = en; 
 shortcut.style.top = (cityWrapper.clientHeight - shortcut.clientHeight) / 2 + 'px'; 
 scroll = new window.BScroll(cityWrapper, { 
 probeType: 3 //1 会截流,只有在滚动结束的时候派发一个 scroll 事件。2在手指 move 的时候也会实时派发 scroll 事件，不会截流。 3除了手指 move 的时候派发scroll事件，在 swipe（手指迅速滑动一小段距离）的情况下，列表会有一个长距离的滚动动画，这个滚动的动画过程中也会实时派发滚动事件 
 }); 
 scroll.scrollTo(0, 0); 
}

function bindEvent() { 
 var touch = {}; 
 var firstTouch; 
 shortcut.addEventListener('touchstart', function (e) { 
 var anchor = e.target.getAttribute('data-anchor'); 
 firstTouch = e.touches[0]; 
 touch.y1 = firstTouch.pageY; 
 touch.anchor = anchor; 
 scrollTo(anchor); 
 }); 
 shortcut.addEventListener('touchmove', function (e) { 
 firstTouch = e.touches[0]; 
 touch.y2 = firstTouch.pageY; 
 var anchorHeight = 16; 
 var delta = (touch.y2 - touch.y1) / anchorHeight | 0; 
 var anchor = shortcutList[shortcutList.indexOf(touch.anchor) + delta]; 
 scrollTo(anchor); 
 e.preventDefault(); 
 e.stopPropagation(); 
 }); 
 function scrollTo(anchor) { 
 var maxScrollY = cityWrapper.clientHeight - cityScroller.clientHeight; 
 var y = Math.min(0, Math.max(maxScrollY, anchorMap[anchor])); 
 if (typeof y !== 'undefined') { 
 scroll.scrollTo(0, y); 
 } 
 } 
}

initCities(); 
bindEvent();