js实现移动端导航点击自动滑动效果

/* 
 * 移动端模拟导航可点击自动滑动 0.1.4 
 * Date: 2017-01-11 
 * by: xiewei 
 * 导航可左右滑动，可点击边缘的一个，自动滚动下一个到可视范围【依赖于iscroll.js】 
 */ 
(function ($) { 
 $.fn.navbarscroll = function (options) { 
  //各种属性、参数 
  var _defaults = { 
   className:'cur', //当前选中点击元素的class类名 
   clickScrollTime:300, //点击后滑动时间 
   duibiScreenWidth:0.4, //单位以rem为准，默认为0.4rem 
   scrollerWidth:3, //单位以px为准，默认为3,[仅用于特殊情况：外层宽度因为小数点造成的不精准情况] 
   defaultSelect:0, //初始选中第n个，默认第0个 
   fingerClick:0, //目标第0或1个选项触发,必须每一项长度一致，方可用此项 
   endClickScroll:function(thisObj){}//回调函数 
  } 
  var _opt = $.extend(_defaults, options); 
  this.each(function () { 
   //插件实现代码 
   var _wrapper = $(this); 
   var _win = $(window); 
   var _win_width = _win.width(),_wrapper_width = _wrapper.width(),_wrapper_off_left = _wrapper.offset().left; 
   var _wrapper_off_right=_win_width-_wrapper_off_left-_wrapper_width; 
   var _obj_scroller = _wrapper.children('.scroller'); 
   var _obj_ul = _obj_scroller.children('ul'); 
   var _obj_li = _obj_ul.children('li'); 
   var _scroller_w = 0; 
   _obj_li.css({"margin-left":"0","margin-right":"0"}); 
   for (var i = 0; i < _obj_li.length; i++) { 
    _scroller_w += _obj_li[i].offsetWidth; 
   } 
   _obj_scroller.width(_scroller_w+_opt.scrollerWidth); 
   var myScroll = new IScroll('#'+_wrapper.attr('id'), { 
    eventPassthrough: true, 
    scrollX: true, 
    scrollY: false, 
    preventDefault: false 
   }); 
   _init(_obj_li.eq(_opt.defaultSelect)); 
   _obj_li.click(function(){ 
    _init($(this)); 
   }); 
   //解决PC端谷歌浏览器模拟的手机屏幕出现莫名的卡顿现象，滑动时禁止默认事件（2017-01-11） 
   _wrapper[0].addEventListener('touchmove',function (e){e.preventDefault();},false); 
   function _init(thiObj){ 
    var $this_obj=thiObj; 
    var duibi=_opt.duibiScreenWidth*_win_width/10,this_index=$this_obj.index(),this_off_left=$this_obj.offset().left,this_pos_left=$this_obj.position().left,this_width=$this_obj.width(),this_prev_width=$this_obj.prev('li').width(),this_next_width=$this_obj.next('li').width(); 
    var this_off_right=_win_width-this_off_left-this_width; 
    if(_scroller_w+2>_wrapper_width){ 
     if(_opt.fingerClick==1){ 
      if(this_index==1){ 
       myScroll.scrollTo(-this_pos_left+this_prev_width,0, _opt.clickScrollTime); 
      }else if(this_index==0){ 
       myScroll.scrollTo(-this_pos_left,0, _opt.clickScrollTime); 
      }else if(this_index==_obj_li.length-2){ 
       myScroll.scrollBy(this_off_right-_wrapper_off_right-this_width,0, _opt.clickScrollTime); 
      }else if(this_index==_obj_li.length-1){ 
       myScroll.scrollBy(this_off_right-_wrapper_off_right,0, _opt.clickScrollTime); 
      }else{ 
       if(this_off_left-_wrapper_off_left-(this_width*_opt.fingerClick)<duibi){ 
        myScroll.scrollTo(-this_pos_left+this_prev_width+(this_width*_opt.fingerClick),0, _opt.clickScrollTime); 
       }else if(this_off_right-_wrapper_off_right-(this_width*_opt.fingerClick)<duibi){ 
        myScroll.scrollBy(this_off_right-this_next_width-_wrapper_off_right-(this_width*_opt.fingerClick),0, _opt.clickScrollTime); 
       } 
      } 
     }else{ 
      if(this_index==1){ 
       myScroll.scrollTo(-this_pos_left+this_prev_width,0, _opt.clickScrollTime); 
      }else if(this_index==_obj_li.length-1){ 
       if(this_off_right-_wrapper_off_right>1||this_off_right-_wrapper_off_right<-1){ 
        myScroll.scrollBy(this_off_right-_wrapper_off_right,0, _opt.clickScrollTime); 
       } 
      }else{ 
       if(this_off_left-_wrapper_off_left<duibi){ 
        myScroll.scrollTo(-this_pos_left+this_prev_width,0, _opt.clickScrollTime); 
       }else if(this_off_right-_wrapper_off_right<duibi){ 
        myScroll.scrollBy(this_off_right-this_next_width-_wrapper_off_right,0, _opt.clickScrollTime); 
       } 
      } 
     } 
    } 
    $this_obj.addClass(_opt.className).siblings('li').removeClass(_opt.className); 
    _opt.endClickScroll.call(this,$this_obj); 
   } 
  }); 
 }; 
})(jQuery);