jquery仿百度经验滑动切换浏览效果

$(function() {
  wordStrong();
  $("#content ul").width($("#content ul li:first").width()*$("#content ul li").length);
  $("#header .top_right .vote").hover(function() {
    $(this).children(".hover-tip").css("display", "block");
    $(this).children(".num").css("display", "none");  
  }, function() {
    $(this).children(".hover-tip").css("display", "none");
    $(this).children(".num").css("display", "block");  
  });
   
   
  $("#content .left, #content .right").width(($(document).width()-$("#content").width())/4);
  $("#content .left").css("left", -$("#content .left").width());
  $("#content .right").css("right", -$("#content .right").width());
   
  var showId = 0;
  $("#content span.left").hover(function() {
    if ( checkFirst() ) return ;
    $(this).css("cursor", "pointer");
    $(this).siblings(".sl").stop().animate({
      opacity:0.5 
    }); 
  }, function() {
    $(this).siblings(".sl").stop().animate({
      opacity:0
    }); 
  }).click(function() {
    if ( checkFirst() ) return ;
    showId --;
    $("#content").attr("showId", showId);
    $("#footer li").children().removeClass("active").end().children().eq(showId).addClass("active");
    center(showId);
  });
   
  $("#content span.right").hover(function() {
    if ( checkLast() ) return ;
    $(this).css("cursor", "pointer");
    $(this).siblings(".sr").stop().animate({
      opacity:0.5
    }); 
  }, function() {
    $(this).siblings(".sr").stop().animate({
      opacity:0
    }); 
  }).click(function() {
    if ( checkLast() ) return ;  
    showId ++;   
    $("#content").attr("showId", showId);
    $("#footer li").children().removeClass("active").end().children().eq(showId).addClass("active");
    center(showId); 
  });
   
  function checkFirst() {
    if ( $("#content").attr("showId") == 0 ) {
      $("#content span.left").css("cursor", "default");
      return true;    
    }
    return false;
  }
   
  function checkLast() {
    if ( $("#content").attr("showId") == $("#content ul li").length-1 ) {
      $("#content span.right").css("cursor", "default");
      return true;    
    }
    return false;  
  }
     
  /* 首字母大写 */
  function wordStrong() {
    var liList = $("#content ul li");
    for (var j = 0; j < liList.length; j ++) {
      var pList = $("#content .cont_"+(j+1)+" .cont_word p");
      for (var i = 0; i < pList.length; i ++) {
        var p = pList.get(i);
        var pCont = $(p).html();    
        var s = $("<b>"+(i+1)+"</b>");
        s.css("font-size", "24px");   
        $(p).html('');
        s.appendTo(p);
        $(p).append(pCont.substring(1));    
      }
    }
  }  
   
  center(0);
   
  //相对li居中
  function center(liIndex) {
    var li = $("#content ul li").css("opacity", 0.3).eq(liIndex).css("opacity", 1);
    $("#content ul").animate({
      left: (-li.width()*liIndex)
    });
  }
   
  var footLen = $("#content ul li").length;
  var foots = $("#footer ul");
  for (var i = 1; i < footLen-1; i ++) {
    var childA = $("<a>").html(i);
    childA.attr("href", "#");
    $("<li>").append(childA).insertBefore(foots.children("[step=last]")).attr("step", i);   
  }
  foots.children(":last").attr("step", footLen-1);
  foots.css("left", ($(window).width()-foots.width())/2); 
  $("#footer li").click(function() {
    $("#footer ul li").children().removeClass("active");
    $(this).children().addClass("active");
    center($(this).attr("step"));
  });
   
  function myAddEvent(obj, e, fn) {
    if ( obj.attachEvent ) {
      obj.attachEvent('on'+e, fn);
    }else obj.addEventListener(e, fn, false);
  }
   
  function onMouseWheel(ev) { 
    var ev = ev||event;   
    //IE
    //wheelDelta  下滚：负， 上滚：下
    //alert(oEvent.wheelDelta);
    //FF
    /https://img.qb5200.com/download-x/detail:  下滚:正, 上滚: 负
    //alert(oEvent.detail)   
    var bDown = true;
    if ( ev.wheelDelta ) {
      bDown = ev.wheelDelta<0;
    }else {
      bDown = ev.detail>0;
    }    
    if ( !bDown ) {
      if ( checkFirst() ) return ;
      showId --;     
    }
    else {
      if ( checkLast() ) return ;
      showId ++;     
    }
    $("#content").attr("showId", showId);
    $("#footer ul li").children().removeClass("active").end().eq(showId).children().addClass("active");
    center(showId);
    if ( oEvent.preventDefault ) {
      oEvent.preventDefault();
    }
    return false;
  }
   
  myAddEvent(window, 'mousewheel', onMouseWheel);
  myAddEvent(window, 'DOMMouseScroll', onMouseWheel);
});