<template>
 <div class="qz-home">
  <div class="quiz-container">
   <div class="quiz-ad-pic" id="pagetop"></div>
   <div class="quiz-main">
    <div class="quiz-main-inside" id="js-content">
     <quiz-sessions class="item" id="quizhall"></quiz-sessions>
     <quizRecords class="item" id="quizrecord"></quizRecords>
     <quiz-history class="item" id="quizHistory"></quiz-history>
     <quiz-mine class="item" id="quizMine"></quiz-mine>
     <quiz-rank class="item" id="quizRank"></quiz-rank>
     <quiz-rule class="item" id="quizRule"></quiz-rule>
    </div>
   </div>
   <navigation id="js-nav"></navigation>
  </div>
 </div>
</template>

<template>
 <nav class="nav-container">
  <div class="nav-mark"></div>
  <div class="nav-main">
   <ul class="nav-list">
    <li :class="{'cur': curindex === index}" v-for="(item, index) in navList" :key="index" :data-id="item.id"><a @click="linkTo(item.id, index)">{{item.name}}</a></li>
   </ul>
   <div class="backtop" @click="backTop()">
    <a></a>
   </div>
  </div>
 </nav>
</template>

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");
      }
     }
    }
   })
  }
 }
};