Implementation of WeChat applet slide left to delete function

<view class="container">
 <view class="touch-item {{item.isTouchMove ? &#39;touch-move-active&#39; : &#39;&#39;}}" data-index="{{index}}" bindtouchstart="touchstart" bindtouchmove="touchmove" wx:for="{{items}}" wx:key="">
  <view class="content">{{item.content}}</view>
  <view class="del" catchtap="del" data-index="{{index}}">删除</view>
 </view>
</view>

.touch-item {
 font-size: 14px;
 display: flex;
 justify-content: space-between;
 border-bottom:1px solid #ccc;
 width: 100%;
 overflow: hidden
}
.content {
 width: 100%;
 padding: 10px;
 line-height: 22px;
 margin-right:0;
 -webkit-transition: all 0.4s;
 transition: all 0.4s;
 -webkit-transform: translateX(90px);
 transform: translateX(90px);
 margin-left: -90px
}
.del {
 background-color: orangered;
 width: 90px;
 display: flex;
 flex-direction: column;
 align-items: center;
 justify-content: center;
 color: #fff;
 -webkit-transform: translateX(90px);
 transform: translateX(90px);
 -webkit-transition: all 0.4s;
 transition: all 0.4s;
}
.touch-move-active .content,
.touch-move-active .del {
 -webkit-transform: translateX(0);
 transform: translateX(0);
}

var app = getApp()
Page({
 data: {
  items: [],
  startX: 0, //开始坐标
  startY: 0
 },
 onLoad: function () {
  for (var i = 0; i < 10; i++) {
   this.data.items.push({
    content: i + " 向左滑动删除哦,向左滑动删除哦,向左滑动删除哦,向左滑动删除哦,向左滑动删除哦",
    isTouchMove: false //默认全隐藏删除
   })
  }
  this.setData({
   items: this.data.items
  })
 },
 //手指触摸动作开始 记录起点X坐标
 touchstart: function (e) {
  //开始触摸时 重置所有删除
  this.data.items.forEach(function (v, i) {
   if (v.isTouchMove)//只操作为true的
    v.isTouchMove = false;
  })
  this.setData({
   startX: e.changedTouches[0].clientX,
   startY: e.changedTouches[0].clientY,
   items: this.data.items
  })
 },
 //滑动事件处理
 touchmove: function (e) {
  var that = this,
   index = e.currentTarget.dataset.index,//当前索引
   startX = that.data.startX,//开始X坐标
   startY = that.data.startY,//开始Y坐标
   touchMoveX = e.changedTouches[0].clientX,//滑动变化坐标
   touchMoveY = e.changedTouches[0].clientY,//滑动变化坐标
   //获取滑动角度
   angle = that.angle({ X: startX, Y: startY }, { X: touchMoveX, Y: touchMoveY });
  that.data.items.forEach(function (v, i) {
   v.isTouchMove = false
   //滑动超过30度角 return
   if (Math.abs(angle) > 30) return;
   if (i == index) {
    if (touchMoveX > startX) //右滑
     v.isTouchMove = false
    else //左滑
     v.isTouchMove = true
   }
  })
  //更新数据
  that.setData({
   items: that.data.items
  })
 },
 /**
  * 计算滑动角度
  * @param {Object} start 起点坐标
  * @param {Object} end 终点坐标
  */
 angle: function (start, end) {
  var _X = end.X - start.X,
   _Y = end.Y - start.Y
  //返回角度 /Math.atan()返回数字的反正切值
  return 360 * Math.atan(_Y / _X) / (2 * Math.PI);
 },
 //删除事件
 del: function (e) {
  this.data.items.splice(e.currentTarget.dataset.index, 1)
  this.setData({
   items: this.data.items
  })
 }
})