 bug  es5.js  #53  

`MemberExpression (nodeIterator) {
    const obj = nodeIterator.traverse(nodeIterator.node.object)
    const name = nodeIterator.node.property.name
    return obj[name]
  }`

53行应为：const name = getPropertyName(nodeIterator.node, nodeIterator)  
否则，某些情况下会出错误
 