解释器模式：对于一种语言，给出其文法表示形式，并定义一种解释器，通过使用这种解释器来解释语言中定义的句子
使用场景：统计页面中点击事件粗发元素在页面所处的路径。

代码实现

  <div id="container">
    <div>
      <div>
        <ul>
          <li><span id="span1"></span></li>
          <li><span id="span2"></span></li>
        </ul>
      </div>
    </div>
    <div>
      <div>
        <ul>
          <li><span id="span5"></span></li>
          <li><span id="span6"></span></li>
        </ul>
      </div>
    </div>
  </div>
  <script>
    // xPath解释器
    var Interpreter = (function () {
      // 获取兄弟元素名称
      function getSulingName(node) {
        if (node.previousSibling) {
          var name = '',
            count = 1,
            nodeName = node.nodeName,
            sibling = node.previousSibling
          while (sibling) {
            if (sibling.nodeType == 1 && sibling.nodeType === node.nodeType && sibling.nodeName) {
              // 如果节点名称和前一个兄弟元素名称相同
              if (nodeName == sibling.nodeName) {
                name += ++count
              } else {
                count = 1
                name += '|' + sibling.nodeName.toUpperCase()
              }
            }
            sibling = sibling.previousSibling
          }
          return name
        } else {
          return ''
        }
      }
      return function (node, wrap) {
        var path = [],
          wrap = wrap || document
        if (node == wrap) {
          if (wrap.nodeType == 1) {
            path.push(wrap.nodeName.toUpperCase())
          }
          return path
        }
        if (node.parentNode !== wrap) {
          path = arguments.callee(node.parentNode, wrap)
        }
        else {
          if (wrap.nodeType == 1) {
            path.push(wrap.nodeName.toUpperCase())
          }
        }
        var sublingsNames = getSulingName(node)
        if (node.nodeType == 1) {
          path.push(node.nodeName.toUpperCase() + sublingsNames)
        }
        return path
      }
    })()
    var path = Interpreter(document.getElementById('span5'))
    console.log(path)
  </script>