export default {
 name: "Navigation",
 data() {
  return {
   navList: [
    { name: "竞猜大厅", id: "quizhall" },
    { name: "竞猜记录", id: "quizrecord" },
    { name: "历史赛事", id: "quizHistory" },
    { name: "我的竞猜", id: "quizMine" },
    { name: "排行榜", id: "quizRank" },
    { name: "玩法", id: "quizRule" }
   ],
   curindex: 0
  };
 },
 mounted() {
  this.initScroll();
 },
 methods: {
  initScroll() {
   window.addEventListener('scroll', function() {
    // 封装类名函数集：判断、移除、增加、获取（简单粗暴版）；
    function removeClass(obj, cls) {
     if (obj.className == cls) {
      obj.className = "";
     }
    }
    function addClass(obj, cls) {
     if (obj.className != cls) {
      obj.className = cls;
     }
    }

    let pos = document.documentElement.scrollTop;
    if (pos > 300) {
     document.querySelector('.nav-container').style.display = 'block';
    } else {
     document.querySelector('.nav-container').style.display = 'none';
    }
    var menus = document.getElementById("js-nav").getElementsByTagName("li");
    var items = document.getElementById("js-content").querySelectorAll(".item");
    var currentId = "";
    
    for (var i = 0; i < items.length; i++) {
     var _item = items[i];
     var _itemTop = _item.offsetTop;
     if (pos > _itemTop - 200) {
      currentId = _item.id;
     } else {
      break;
     }
    }
    if (currentId) {
     for (var j = 0; j < menus.length; j++) {
      var _menu = menus[j];
      // href属性获取的是整个link，需以#为界截除获取最后一个元素；
      var _href = _menu.getAttribute('data-id');
      if (_href != currentId) {
       removeClass(_menu, "cur");
      } else {
       addClass(_menu, "cur");
      }
     }
    }
   })
  }
 }
};