ios10禁止用户缩放

<script>
  window.onload=function () {
    document.addEventListener('touchstart',function (event) {
      if(event.touches.length>1){
        event.preventDefault();
      }
    })
    var lastTouchEnd=0;
    document.addEventListener('touchend',function (event) {
      var now=(new Date()).getTime();
      if(now-lastTouchEnd<=300){
        event.preventDefault();
      }
      lastTouchEnd=now;
    },false)
  }
</script>