The data in mongodb acquired by vue is initially undefined, but it can still be rendered.

  mongodb, question
[Vue warn]: Error when evaluating expression "topic.meta.createAt !  = topic.meta.updateAt": TypeError: Cannot read property 'createAt' of undefined (found in component: <v-article>)
 
 [Vue warn]: Error when evaluating expression "topic.meta.createAt": TypeError: Cannot read property 'createAt' of undefined (found in component: <v-article>)

This is the error message, the following is my code part.

<h1>{{ topic.title }}</h1>
 <div class="info">
 <a v-for="tag in topic.tag" v-link="{name: 'tab', params: {tab: tag, page: 1}}" class="tag">
 {{ tag | convertTag}}
 </a>
 <a class="name"><strong>radical</strong></a>
 <span class="ask">{{ topic.meta.createAt | timeToNow }}&nbsp;  Publish < /span >
 <span v-if="topic.meta.createAt !  = topic.meta.updateAt" class="update">{{ topic.meta.updateAt | timeToNow }}&nbsp;  Update < /span >
 </div>

This is a component topic that I will get through my getters. I request data from mongodb through actions, and everything looks normal. . .
ConvertTag and timeToNow are both filter i wrote myself.

In this way, you should first judge the existence of the topic.meta object to remove its attributes, so as not to report an error.
The reason for reporting errors is that you get meta data when you don’t get its properties.

<h1>{{ topic.title }}</h1>
 <div class="info">
 <a v-for="tag in topic.tag" v-link="{name: 'tab', params: {tab: tag, page: 1}}" class="tag">
 {{ tag | convertTag}}
 </a>
 <a class="name"><strong>radical</strong></a>
 <span v-if="!  !  topic.meta" class="ask">{{ topic.meta.createAt | timeToNow }}&nbsp;  Publish < /span >
 <span v-if="!  !  topic.meta && topic.meta.createAt !  = topic.meta.updateAt" class="update">{{ topic.meta.updateAt | timeToNow }}&nbsp;  Update < /span >
 </div>