code: function parseExprProxy(code, scopes, data, tokens) {
          if (Array.isArray(tokens)) {
              var array = tokens.map(function(token) {
                  var tmpl = {}
                  return token.expr ? parseExpr(token.value, scopes, tmpl) || tmpl : token.value
              })
  
              data.evaluator = function() {
                  var ret = ""
                  for (var i = 0, el; el = array[i++]; ) {
                      ret += typeof el === "string" ? el : el.evaluator.apply(0, el.args)
                  }
                  return ret
              }
              data.args = []
          } else {
              parseExpr(code, scopes, data, tokens)
          }
          if (data.evaluator) {
              data.handler = bindingExecutors[data.handlerName || data.type]
              data.evaluator.toString = function() {
                  return data.type + " binding to eval(" + code + ")"
              }
              //方便调试
              //这里非常重要,我们通过判定视图刷新函数的element是否在DOM树决定
              //将它移出订阅者列表
              registerSubscriber(data)
          } else {
              if (data.nodeType === 3) {
                  data.node.data = openTag + data.value + closeTag
              }
          }
      }
docs: parseExpr的智能引用代理