iframe加载闪过白块问题

在使用iframe时，iframe背景为白块，刷新时也会闪过白块。如果刷新时间长，就会一直出现白块；以下是再vue中，再js中同样适用；

<div v-else ref="iframeWanner" v-loading="loading">
  <iframe
    style="border:none"
    width="100%"
    allowtransparency="true"
    :style=" { visibility:visibiShow }"
    :height= iframeHei
    ref="iframe"
    v-bind:src="reportUrl"
  ></iframe>
</div>

if (!/*@cc_on!@*/0) { // if not IE  判断不是ie
  iframe.onload = function() {
    that.visibiShow = 'visible'
    that.loading = false
  }
} else {
  iframe.onreadystatechange = function() {
    if (iframe.readyState === 'complete') {
      that.visibiShow = 'visible'
      that.loading = false
    }
  };
}