handleMouseDown (event) {
      if (this.isDisabled) return
      this.$emit('mousedown', event)
      event.preventDefault()

      const newValue = this.getNewValue(event)
      if (newValue !== this.actualValue) {
        this.updateValue(newValue)
      }

      document.body.addEventListener('mousemove', this.handleMouseMove)
      document.body.addEventListener('touchmove', this.handleMouseMove)
      document.body.addEventListener('mouseup', this.handleMouseUp)
      document.body.addEventListener('touchend', this.handleMouseUp)
      this.thumbNode && this.thumbNode.focus()
    }
Handles mousedown event for slider
@param {Event} event