ios10之后的H5禁止缩放

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