A custom directive similar to v-if in vuejs

问题

I'm writing a custom directive in vue.

I want it to work like v-if but it will have a little logic going inside it. Let me explain with an example:

<button v-permission="PermissionFoo">Do Foo</button>

It will check the permission and will show or hide the component.

Currently I'm doing this via CSS styles:

var processPermissionDirective = function (el, binding, vnode) {
    if (SOME_LOGIC_HERE) {
        el.style.display = el._display;
    }
    else {
        el.style.display = 'none';
    }
}

export default {
    bind: function (el, binding, vnode) {
        el._display = el.style.display;
        processPermissionDirective(el, binding, vnode);
    },
    update: function (el, binding, vnode) {
        processPermissionDirective(el, binding, vnode);
    }
}

But I don't want this element to stay in the document. So I'm looking for another way other than CSS because it must be also removed from DOM like v-if does.

回答1:

Try to use this hack:

Vue.directive('permission', (el, binding, vnode) => {
  if (!isUserGranted(binding.value)) {
    // replace HTMLElement with comment node
    const comment = document.createComment(' ');
    Object.defineProperty(comment, 'setAttribute', {
      value: () => undefined,
    });
    vnode.elm = comment;
    vnode.text = ' ';
    vnode.isComment = true;
    vnode.context = undefined;
    vnode.tag = undefined;
    vnode.data.directives = undefined;

    if (vnode.componentInstance) {
      vnode.componentInstance.$el = comment;
    }

    if (el.parentNode) {
      el.parentNode.replaceChild(comment, el);
    }
  }
});

UPD 05-19-2017: My latest code. I define setAttribute() and check for vnode.componentInstance to prevent js errors when using with both html elements and Vue components.

来源：https://stackoverflow.com/questions/43003976/a-custom-directive-similar-to-v-if-in-vuejs

标签

vuejs2

vuejs-directive