是否可以检测iPhone上的网页中是否启用了VoiceOver？

if (navigator.userAgent.indexOf('iPhone') !== -1 && navigator.userAgent.indexOf('iPod') !== -1 && navigator.userAgent.indexOf('iPad') !== -1) {
  // VoiceOver is enabled
} else {
  // VoiceOver is not enabled
}

body {
  /* Setting the default font size to 16px */
  font-size: 16px;
}

/* Override the font size for elements with the "voicemail" class */
.voicemail {
  font-size: 24px;
}