原生JS如何实现多条件筛选的方法

<div id="direction">
  <strong>方向：</strong>
  <span class="active">全部</span>
  <span>前端</span>
  <span>后台</span>
  <span>数据库</span>
  <span>UI设计</span>
</div>
<div id="category">
  <strong>分类：</strong>
  <span class="active">全部</span>
  <span>HTML/CSS</span>
  <span>JavaScript</span>
  <span>jQuery</span>
  <span>Python</span>
  <span>Java</span>
  <span>AngularJS</span>
</div>
<div id="type">
  <strong>类型：</strong>
  <span class="active">全部</span>
  <span>基础</span>
  <span>案例</span>
  <span>框架</span>
  <span>工具</span>
</div>
<strong>返回值：</strong>
<p id="Res"></p>

<style>
  span{display: inline-block;
    cursor: pointer; padding: 8px; border: 1px solid #999;}
  span.active{
    background-color: #c14d00;
  }
</style>

<script>
  var dSpan = document.getElementById('direction').getElementsByTagName('span');
  var cSpan = document.getElementById('category').getElementsByTagName('span');
  var tSpan = document.getElementById('type').getElementsByTagName('span');
  var aSpan = document.getElementsByTagName('span');
  var oDirection = document.getElementById('direction');
  var oCategory = document.getElementById('category');
  var oType = document.getElementById('type');
  var oRes = document.getElementById('Res');
  dSpan[0].className = 'active';
  cSpan[0].className = 'active';
  tSpan[0].className = 'active';
  for(var i=0; i<aSpan.length; i++){
    aSpan[i].onclick = function(){
      var siblings = this.parentNode.children;
      for(var j=0; j<siblings.length; j++){
        siblings[j].className = '';
      }
      this.className = 'active';
      if(this.parentNode == oDirection || this.parentNode == oCategory || this.parentNode == oType){
        returnRes();
      }
    }
  }

  function returnRes(){
    var o1 = 0, o2 = 0, o3 = 0;
    for(var i=0; i<dSpan.length; i++){
      if(dSpan[i].className == 'active'){
        o1 = i;
      }
    }
    for(var i=0; i<cSpan.length; i++){
      if(cSpan[i].className == 'active'){
        o2 = i;
      }
    }
    for(var i=0; i<tSpan.length; i++){
      if(tSpan[i].className == 'active'){
        o3 = i;
      }
    }
    oRes.innerHTML = (dSpan[o1].innerHTML + "," + cSpan[o2].innerHTML + "," + tSpan[o3].innerHTML);
  }
</script>