iframe.vue

<script>
    directives: {
      'inner-height': {
        bind: function() {
          this.el.addEventListener('load', () => {
            var doc = this.el.contentDocument || this.el.contentWindow.document;
            this.el.style.height = doc.body.scrollHeight + 'px';
          });
        }
      }
    }
</script>

<template>

<iframe :srcdoc="quest.selectedQuestion.syakyo_html"
        scrolling="no"
        v-inner-height></iframe>

</template>