Mutating warn

HTML

<html>

  <head>
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
  </head>

  <body>
    <div>
      <div id="app">
        <string-bar :inner-text="appText"></string-bar>
      </div>
    </div>


    <script>
      Vue.component('string-bar', {
        props: ['innerText'],
        data: function() {return {text: this.innerText}},
        template: '<input type="text" v-model="text">'
      });

      var app = new Vue({
        el: '#app',
        data: {
          appText: 'some text'
        }
      });

    </script>
  </body>

</html>