code: function setProperties(el, binding) {
    el.popper._appendToBody = !(binding.value.appendToBody === false);
    if (binding.modifiers.always) {
      el.popper._always = binding.modifiers.always;
    }
    if (binding.modifiers.controlled) {
      el.popper._controlled = binding.modifiers.controlled;
    }
    if (binding.modifiers.ellipsis) {
      el.popper._ellipsis = binding.modifiers.ellipsis;
    }
    if (typeof binding.value === 'object') {
      el.popper._content = binding.value.content || '';
      el.popper._delay = binding.value.delay;
      el.popper._disabled = binding.value.disabled;
    } else if (typeof binding.value === 'string') {
      el.popper._content = binding.value;
    } else {
      el.popper._content = binding.expression;
    }
  }
docs: 通过指令参数设置popper的属性