1. let startx, starty
    2. // 获得角度
    3. function getAngle (angx, angy) {
    4.   return Math.atan2(angy, angx) * 180 / Math.PI
    5. }
    7. // 根据起点终点返回方向 1向上 2向下 3向左 4向右 0未滑动
    8. function getDirection (startx, starty, endx, endy) {
    9.   const angx = endx - startx
    10.   const angy = endy - starty
    11.   let result = 0
    13.   // 如果滑动距离太短
    14.   if (Math.abs(angx) < 2 && Math.abs(angy) < 2) {
    15.     return result
    16.   }
    18.   const angle = getAngle(angx, angy)
    19.   if (angle >= -135 && angle <= -45) {
    20.     result = 1
    21.   } else if (angle > 45 && angle < 135) {
    22.     result = 2
    23.   } else if ((angle >= 135 && angle <= 180) || (angle >= -180 && angle < -135)) {
    24.     result = 3
    25.   } else if (angle >= -45 && angle <= 45) {
    26.     result = 4
    27.   }
    29.   return result
    30. }
    31. // 手指接触屏幕
    32. document.addEventListener('touchstart', function (e) {
    33.   startx = e.touches[0].pageX
    34.   starty = e.touches[0].pageY
    35. }, false)
    36. // 手指离开屏幕
    37. document.addEventListener('touchend', function (e) {
    38.   const endx = e.changedTouches[0].pageX
    39.   const endy = e.changedTouches[0].pageY
    40.   const direction = getDirection(startx, starty, endx, endy)
    41.   switch (direction) {
    42.   case 0:
    43.     alert('未滑动！')
    44.     break
    45.   case 1:
    46.     alert('向上！')
    47.     break
    48.   case 2:
    49.     alert('向下！')
    50.     break
    51.   case 3:
    52.     alert('向左！')
    53.     break
    54.   case 4:
    55.     alert('向右！')
    56.     break
    57.   default:
    58.   }
    59. }, false)