关于封装的Slider的问题

// JavaScript Document
function Slider(el,options){
	var defaults={
		initIndex:0,
		speed:300,
		hasIndicator:false
	};
	//获取用户传入的数据，如有就用用户的，如没有就用设定的值
	this.options={};
	this.options.initIndex=typeof options.initIndex!=='undefined'?options.initIndex:defaults.initIndex;
	this.options.speed=typeof options.speed!=='undefined'?options.speed:defaults.speed;
	this.options.hasIndicator=typeof options.hasIndicator!=='undefined'?options.hasIndicator:defaults.hasIndicator;
	
	//获取元素
	this.el=el;
	this.itemContainer=el.querySelector('.slider-item-container');
	this.items=this.itemContainer.children;
	this.distancePerSlide=this.items[0].offsetWidth;//一张图片的宽度
	
	//索引值
	this.minIndex=0;
	this.maxIndex=this.items.length-1;
	//this.index=this.options.initIndex;//如：这样写，当用户写的值为10，就会出错
	this.index=this._adjustIndex(this.options.initIndex);
	
	this.move(this.getDistanceByIndex(this.index));//调用移动函数移动幻灯片
	
	if(this,options.hasIndicator){//根据用户的需求判断是否创建指示器，并进行切换
		this._createIndicators();
		this._seteIndicatorActive(this.index);
	}
}
Slider.prototype.to=function(index){//带有动画的切换
	this.index=index;
	
	this._setTransitionSpeed(this.options.speed);
	this.move(this.getDistanceByIndex(this.index));//调用移动函数移动幻灯片
	
	var self=this;
	this.itemContainer.addEventListener('transitionend',function(){
		self._setTransitionSpeed(0);
	},false);
	
	if(this.options.hasIndicator){
		this._seteIndicatorActive(this.index);   
	}
};
Slider.prototype._setTransitionSpeed=function(speed){//设置transition的速度
	this.itemContainer.style.transitionDuration=speed+'ms';
};
Slider.prototype.prev=function(){//上一张按钮点击执行的函数
	this.to(this.index-1);
};
Slider.prototype.next=function(){//下一张按钮点击执行的函数
	this.to(this.index+1);
};
Slider.prototype._adjustIndex=function(index){//处理索引的函数，防止索引出错
	if(index<this.minIndex){
		index=this.minIndex;   
	}else if(index>this.maxIndex){
		index=this.maxIndex;
	}
	return index;
};
Slider.prototype.move=function(distance){//移动函数，给出距离，然后移动
	this.itemContainer.style.transform='translate3d('+distance+'px,0,0)';
};
Slider.prototype.getDistanceByIndex=function(index){//根据索引值计算移动距离
	return -index*this.distancePerSlide;
};
Slider.prototype._createIndicators=function(index){//创建小圆点，即指示器
	var indicatorContainer=document.createElement('div');
	var html="";
	indicatorContainer.className="slider-indicator-container";
	for(var i=0;i<this.maxIndex+1;i++){
		html+='<span class="slider-indicator"></span>';
	}
	indicatorContainer.innerHTML=html;
	this.el.appendChild(indicatorContainer);
};
Slider.prototype._seteIndicatorActive=function(index){//切换小圆点
	this.indicator=this.indicator||this.el.querySelectorAll('.slider-indicator');//短路操作符是为了防止每次触发_seteIndicatorActive都进行获取，浪费性能
	for(var i=0;i<this.indicator.length;i++){
		this.indicator[i].classList.remove('slider-indicator-active');
	}
	this.indicator[index].classList.add('slider-indicator-active');
};



var slider=new Slider(document.getElementById('slider'),{
	initIndex:2,
	speed:300,
	hasIndicator:true
},false);
document.getElementById('prev').addEventListener("click",function(){
	slider.prev();
},false);
document.getElementById('next').addEventListener("click",function(){
	slider.next();
},false);

1. Slider中写的是this.move(this.getDistanceByIndex(this.index));为什么还是会有动画效果？

   动画效果_setTransitionSpeed写在to里，可调用的是move

2. _adjustIndex中对索引值进行了判断，为什么当我移动到边界时，如移动到第一张图片，索引值为0，继续往左移动还是可以移动？并且会报错