title: d3 chart update automatically when data change by using vue
body: <p>I want every time my mock changes and paesss to dataa, the barchart can re-render or updated. I watch dataa in barchart component, but it didn't work.
   "console.log('this', this.dataa);" never trigger. I have no idea which part is wrong.</p>
  
  <p>here is my code:</p>
  
  <pre><code>&lt;sr-bar-chart
   :title= "descriptionText.title_traffic"
   :dataa= "mock"
   :unit="descriptionText.avg7d_unit_people"
   :index="'1'"
   :barColor="'#adadad'"
  </code></pre>
  
  <p>and in bar chart component</p>
  
  <pre><code>export default {
   name: 'sceneBarChart',
   props: ['title', 'dataa', 'unit', 'index', 'barColor'],
    data() {
    return {
      count: 0
    };
  },
  watchers: {
    dataa() {
      console.log('this', this.dataa);
      this.drawMap();
    }
   },
   methods: {
    drawMap() {
     ....
    }
   },
   mounted() {
    this.drawMap();
  }
  </code></pre>
  
  <p>};</p>
  
  <p>Thanks!</p>