<style>
 * {
 margin: 0;
 padding: 0;
 }
 html,body,.container {
 width: 100%;
 height: 100%;
 }
 .container>ul>li {
 padding: 15px 20px;
 text-align: center;
 border-bottom: 1px solid #ccc;
 }
</style>

<div id="container" class="container">
 <ul class="scroller">
 <li>item1</li>
 <li>item2</li>
 <li>item3</li>
 <li>item4</li>
 <li>item5</li>
 </ul>
</div>

<script src="https://cdn.bootcss.com/iScroll/5.2.0/iscroll.min.js"></script>
<script>
 var myScroll = null;
 function onLoad() {
 myScroll = new IScroll('container');
 }
 window.addEventListener('DOMContentLoaded', onLoad, false);
</script>

_initEvents: function (remove) {
 // ...
 // 這里省略若干代碼

 if ( utils.hasTouch && !this.options.disableTouch ) {
  eventType(this.wrapper, 'touchstart', this);
  eventType(target, 'touchmove', this);
  eventType(target, 'touchcancel', this);
  eventType(target, 'touchend', this);
 }

 // ...
},

target.addEventListener(type, listener[, options]);
target.addEventListener(type, listener[, useCapture]);
target.addEventListener(type, listener[, useCapture, wantsUntrusted ]); 
// 
// Gecko/Mozilla only

listener

當(dāng)所監(jiān)聽的事件類型觸發(fā)時(shí)，會(huì)接收到一個(gè)事件通知（實(shí)現(xiàn)了 Event 接口的對(duì)象）對(duì)象。listener 必須是一個(gè)實(shí)現(xiàn)了 EventListener 接口的對(duì)象，或者是一個(gè)函數(shù)

var Something = function(element) {
 // |this| is a newly created object
 this.name = 'Something Good';
 this.handleEvent = function(event) {
 console.log(this.name); 
 // 'Something Good', as this is bound to newly created object
 switch(event.type) {
  case 'click':
  // some code here...
  break;
  case 'dblclick':
  // some code here...
  break;
 }
 };

 // Note that the listeners in this case are |this|, not this.handleEvent
 element.addEventListener('click', this, false);
 element.addEventListener('dblclick', this, false);

 // You can properly remove the listeners
 element.removeEventListener('click', this, false);
 element.removeEventListener('dblclick', this, false);
}
var s = new Something(document.body);

handleEvent: function (e) {
 switch ( e.type ) {
  case 'touchstart':
  case 'pointerdown':
  case 'MSPointerDown':
  case 'mousedown':
  this._start(e);
  break;
  case 'touchmove':
  case 'pointermove':
  case 'MSPointerMove':
  case 'mousemove':
  this._move(e);
  break;
  case 'touchend':
  case 'pointerup':
  case 'MSPointerUp':
  case 'mouseup':
  case 'touchcancel':
  case 'pointercancel':
  case 'MSPointerCancel':
  case 'mousecancel':
  this._end(e);
  break;
  // ...
 }
 }
};

if ( !this.enabled || (this.initiated && utils.eventType[e.type] !== this.initiated) {
 return;
}

// ...

var point = e.touches ? e.touches[0] : e,
 pos;

this.initiated = utils.eventType[e.type];
this.moved = false;
initiated屬性在最開始肯定是沒有的，而enabled默認(rèn)是true，所以在最開始執(zhí)行這個(gè)方法的時(shí)候是不會(huì)返回的，而是會(huì)給initiated這個(gè)屬性設(shè)置當(dāng)前的eventType值，這個(gè)值會(huì)在_move方法中用到。重點(diǎn)來看看_move方法。

if ( !this.enabled || utils.eventType[e.type] !== this.initiated ) {
 return;
}

if ( timestamp - this.endTime > 300 && (absDistX < 10 && absDistY < 10) ) {
 return;
}

// If you are scrolling in one direction lock the other
if ( !this.directionLocked && !this.options.freeScroll ) {
 if ( absDistX > absDistY + this.options.directionLockThreshold ) {
 this.directionLocked = 'h'; // lock horizontally
 } else if ( absDistY >= absDistX + this.options.directionLockThreshold ) {
 this.directionLocked = 'v'; // lock vertically
 } else {
 this.directionLocked = 'n'; // no lock
 }
}

if ( this.directionLocked == 'h' ) {
 if ( this.options.eventPassthrough == 'vertical' ) {
 e.preventDefault();
 } else if ( this.options.eventPassthrough == 'horizontal' ) {
 this.initiated = false;
 return;
 }

 deltaY = 0;
} else if ( this.directionLocked == 'v' ) {
 if ( this.options.eventPassthrough == 'horizontal' ) {
 e.preventDefault();
 } else if ( this.options.eventPassthrough == 'vertical' ) {
 this.initiated = false;
 return;
 }

 deltaX = 0;
}

deltaX = this.hasHorizontalScroll ? deltaX : 0;
deltaY = this.hasVerticalScroll ? deltaY : 0;

newX = this.x + deltaX;
newY = this.y + deltaY;
// ...

// 這里是移動(dòng)
this._translate(newX, newY);

this.wrapperWidth = this.wrapper.clientWidth;
this.wrapperHeight = this.wrapper.clientHeight;

var rect = utils.getRect(this.scroller);
/* REPLACE START: refresh */

this.scrollerWidth = rect.width;
this.scrollerHeight = rect.height;

this.maxScrollX = this.wrapperWidth - this.scrollerWidth;
this.maxScrollY = this.wrapperHeight - this.scrollerHeight;

/* REPLACE END: refresh */

this.hasHorizontalScroll = this.options.scrollX && this.maxScrollX < 0;
this.hasVerticalScroll = this.options.scrollY && this.maxScrollY < 0;