text: const _Inertia = function (CScroll) {
  
      CScroll.prototype.startInertia = function () {
          //option 设置
          if (!this.$op.inertia) return
          //  双重判断是否开启惯性滑动
          if (this._this.vt < 40 && Math.abs(this._this.vy) > 1 && !this.$op.scrollX) {
              this._this.ine = true
          } else if (this._this.vt < 40 && this.$op.scrollX && Math.abs(this._this.vx) > 1) {
              this._this.ine = true
          }else{
              this._this.ine = false
          }
          // 超出区域禁止惯性滑动
          if (this.outSide()) this._this.ine = false
  
          this.calcInertia()
      }
  
      CScroll.prototype.calcInertia = function () {
          //  计算惯性滑动距离 
          if (this._this.ine) {
              if (this.$op.scrollX) {
                  this._this.friction = (this._this.vt * this._this.vx + this._this.vx) * 0.1
              } else {
                  this._this.friction = (this._this.vt * this._this.vy + this._this.vy) * 0.1
              }
              this.setInertia()
          }
      }
  
      CScroll.prototype.setInertia = function () {
          if (!this.$op.inertia) return
          let a = null
          // 如果friction惯性值小于1 退出函数
          if (Math.abs(this._this.friction) < 1 ) {
              window.cancelAnimationFrame(this.$event.time)
              this.setEase()
              return
          }
          // 如果设置了区域锁 判断
          if(this.sideLock()){
              window.cancelAnimationFrame(this.$event.time)
              this.setEase()
              return
          }
  
  
  
          //判断是否超出内容区
          if (this.outSide()) {
              this._this.friction -= this._this.friction * 0.2
              a = this._this.friction - this._this.friction * 0.2
          } else {
              this._this.friction -= this._this.friction * 0.1
              a = this._this.friction - this._this.friction * 0.1
          }
  
          if (this.$op.scrollX) {
              this.$pos.x += a
          } else {
              this.$pos.y += a
          }
  
          this.setPos()
          this.$event.time = window.requestAnimationFrame(this.setInertia.bind(this))
      }
  }
  
  export default _Inertia
  
  