Per the Vue docs, it's possible to build components in Vue (v3) and package them as native Web Components for use with any framework or none at all.
As I've already found, the gap between design models for Vue components and Web Components can make this complex and sometimes a straight-up bad idea (at what point is it better and more maintainable to just go ahead building fully-native components?)... But let's assume for a moment that it's necessary here.
My question - What's the best way to expose a function-like interface on a Vue-built Web Component (to parent nodes)?
The Vue doc discusses passing in reactive data via props/slots, and publishing CustomEvents from the components, but I don't see mention of
taking function calls (or at a stretch, events) from outside. As far as I can tell this is a pretty strong assumption that data and event flow on the rest of the app/page works in a very "Vue-like way"?
For now, my workaround on this is to look up the host element in onMounted() (as per this question) and just set whatever extra properties are required at that point (hoping they shouldn't be required before the Vue component mounts, because I'm not aware of any external events raised when Vue finishes mounting the custom element).
This way the function can still be defined in the context of, and access variables/etc from, the setup function - but can be called by other elements on the page that only have a reference to the element, not the Vue component.
Can't say I like it much though:
<template>
<div ref="someElInTemplate">...</div>
</template>
<script lang="ts">
interface MyCoolHTMLElement extends HTMLElement {
myCoolFunction: () => void;
}
</script>
<script setup lang="ts">
const someElInTemplate = ref<HTMLElement>();
function myCoolFunction() { }
onMounted(() => {
const hostNode = (
somElInTemplate.value?.getRootNode() as ShadowRoot | undefined
)?.host as MyCoolHTMLElement;
hostNode.myCoolFunction = myCoolFunction;
});
</script>
When I do the Vue quickstart and it creates a HelloWorld application, I see that App.vue line 20 contains this line:
<RouterView />
I can't find any documentation for RouterView. It seems odd that a quickstart / tutorial would include an undocumented tag. I do see router-view, is that the same thing?
The RouterView or router-view component is used to display the component or template that corresponds to the current route.
Source: vue-router.d.ts
/**
* Component to display the current route the user is at.
*/
export declare const RouterView: new () => {
$props: AllowedComponentProps & ComponentCustomProps & VNodeProps & RouterViewProps;
$slots: {
default: (arg: {
Component: VNode;
route: RouteLocationNormalizedLoaded;
}) => VNode[];
};
};
Here is a webpage detailing how to use the RouterView component: How to Use Vue Router's router-view Component
After doing some of my own experimenting, I created a vue app (with Vue Router), I found that my components were not being displayed even if I was at the specified route. After adding the RouterView component to my App.vue template, I was able to see the view that was specified by the route.
Edit:
I'd suggest looking through the following tutorial:
Create your own Vue.js Router. After I created my own router I can now understand why this component is present. The component will render the component that the route specifies, therefore, when the route changes the component rendered will change.
From Vue docs for Component Registration > Name Casing:
When defining a component with PascalCase, you can use either case when referencing its custom element. That means both <my-component-name> and <MyComponentName> are acceptable. Note, however, that only kebab-case names are valid directly in the DOM (i.e. non-string templates).
So <RouterView /> is the same as <router-view />.
When I search for something I came across this post
Here, something, I believe it is component, is defined as below.
export default {
name: 'app',
methods: {
testFunction: function (event) {
console.log('test clicked')
}
},
components: {
Test
}
}
As per the documentation, I came across this
import BaseButton from './BaseButton.vue'
import BaseIcon from './BaseIcon.vue'
import BaseInput from './BaseInput.vue'
export default {
components: {
BaseButton,
BaseIcon,
BaseInput
}
}
I really not sure, whether app is a component which contains Test. Is it the component definition in export? How do we understand that is a component from vue code?
Is it only by the below ways?
Vue.component
components in Vue instance
Not sure - the export default way?
I understand that I sound different because it is Javascript. Could someone help me with this?
There are conventionally, three different types of components in Vue JS.
Root Component
View Component
Normal Component
In a conventional structure the Root component is named 'app' and is passed to the Vue instance when initializing the App for the first time. This component can not be imported and reused inside other components as it will cause a recursive effect. For example this App.vue file is a Root component. It is used inside this main.js file and passed to the Vue instance using new Vue.
The View components are dynamically added or removed from the Root component based on the route. They are written and act as normal component and are only used for Vue router component property. For example the Home and Comments components inside this Router index file are known as View components. They are passed inside the route objects as components inside individual routes. When the app navigates to that particular route, the <router-view> template inside the App.vue file gets replace with the template of the corresponding View component.
Normal components can be used anywhere and are imported by other components. They can be imported inside the View components as well as the Root components. For example, in root component App.vue we see the component Navbar is used. In View component Comments.vue the Replies component is used.
All these components are identical in declaration and behavior but differ in usage.
In PHP when we include code from another file, we include it and that's it, the code is now available to us within the file in which we performed the include. But in Vue.js, after importing a component we must also export it.
Why? Why don't we simply import it?
in Vue.js, after importing a component we must also export it.
I think you might be referring to the following lines in User.vue and wondering why UserDetail and UserEdit are imported into the file and then exported in the script export's components property:
import UserDetail from './UserDetail.vue';
import UserEdit from './UserEdit.vue';
export default {
components: {
appUserDetail: UserDetail,
appUserEdit: UserEdit
}
}
vue-loader expects the script export of a .vue file to contain the component's definition, which effectively includes a recipe to assemble the component's template. If the template contained other Vue components, the definition of the other components would need to be provided, otherwise known as component registration. As #Sumurai8 indicated, the import of the .vue files itself does not register the corresponding single-file-components; rather those components must be explicitly registered in the importer's components property.
For example, if App.vue's template contained <user /> and User.vue were defined as:
<template>
<div class="user">
<app-user-edit></app-user-edit>
<app-user-detail></app-user-detail>
</div>
</template>
<script>
export default {
name: 'user'
}
</script>
...the User component would be rendered blank, and you would see the following console errors:
[Vue warn]: Unknown custom element: <app-user-edit> - did you register the component correctly? For recursive components, make sure to provide the "name" option.
[Vue warn]: Unknown custom element: <app-user-detail> - did you register the component correctly? For recursive components, make sure to provide the "name" option.
demo 1
When Vue attempts to render <user /> inside App.vue's template, Vue doesn't know how to resolve the inner <app-user-detail> and <app-user-edit> because their component registrations are missing. The errors can be resolved by local component registration in User.vue (i.e., the components property shown above).
Alternatively, the errors can be resolved with global component registration of UserDetail and UserEdit, which would obviate the local registration in User.vue. Note that global registration must be done before creating the Vue instance. Example:
// main.js
import Vue from 'vue';
import UserDetail from '#/components/UserDetail.vue';
import UserEdit from '#/components/UserEdit.vue';
Vue.component('app-user-detail', UserDetail);
Vue.component('app-user-edit', UserEdit);
new Vue(...);
demo 2
Components in vue can be tricky. If you haven't yet, I would highly recommend reading the documentation on the vue.js website on how component registration works, specifically, as tony19 mentions global and local registration. The code example you show in your screenshot is actually doing a couple of things. For one, it is making the components available locally, and only locally (as in that .vue file) for use. In addition, it is making it available to the template as the key you provide in the components object, in this case, app-user-detail and app-user-edit instead of user-detail and user-edit.
Importantly, it should be mentioned that an import is not actually required for this component registration to function. You could have multiple components defined in a single file. The components key gives a way to identify what that component is using. So that import isn't required, so vue does require the components key to understand what you are using as a component, and what is just other code.
Finally, as some of the other answers have alluded to, the components key is not actually an export. The default signature of a vue component requires an export but this is not exporting the components listed under the components key. What it is doing is letting vue build in a top down manner. Depending on what the rest of your application setup looks like, you may be using single file components, or not. Either way, vue will start with the top level vue instance and work its way down through components, with the exception of global registration, no top level component knows which components are being used below it.
This means for vue to render things properly, each component has to include a reference to the extra components it uses. This reference is exported as part of the higher level component (in your case User.vue), but is not the component itself (UserDetail.vue).
So it may appear that vue requires a second export after import, but it is actually doing something else to allow the root vue instance to render your component.
As an aside, the vue documentation on this subject really is quite good, if you haven't already please take a look at the sections I linked above. There is an additional section on module import/export systems that seems highly relevant to what you are asking, you can find that here: Module-systems.
import imports code into the current file, but it does not do anything on its own. Imagine the following non-vue code:
// File helpers.js
export function tickle(target) {
console.log(`You tickle ${target}`)
}
// File main.js
import { tickle } from 'helpers'
You have imported the code, but it does not do anything. To actually tickle something, you need to call the function.
tickle('polar bear');
In Vue this works the same. You define a component (or actually just an Object), but the component does not do anything on it's own. You export this component so you can import it in other places where the Vue library can do something with this object.
In a Vue component you export your current component, and import components you use in your template. You generally do the following:
<template>
<div class="my-component">
<custom-button color="red" value="Don't click me" #click="tickle" />
</div>
</template>
<script>
import CustomButton from './CustomButton';
export default {
name: 'my-component',
components: {
CustomButton
}
}
</script>
Your component mentions a component named "custom-button". This is not a normal html element. It does not know what to do with it normally. So what do we do? We import it, then put it in components. This maps the name CustomButton to the component you imported. It now knows how to render the component.
The "magic" happens when you mount the root component using Vue, usually in your main.js.
import Vue from "vue";
import App from "./App";
Vue.config.productionTip = false;
/* eslint-disable no-new */
new Vue({
el: "#app",
components: { App },
template: "<App/>"
});
What does this do? You tell Vue to render <App/> in a html element identified by #app, and you tell that it should find this element in ./App.vue.
But can't we just omit export if the Vue compiler was 'smarter'? Yes, and no. Yes, because a compiler can transform a lot of things into valid javascript, and no because it makes no sense and severely limits what you can do with your component, while also making the compiler more bug-prone, less understandable and overall less useful.
In order for App.vue to be able to use the User-component you need to export the default object of the User.vue-file.
In the export default { you don't actually export the newly imported components. You are just exporting a completely normal JavaScript Object. This object just happens to have a reference to another Object.
When you import an object (or function or array or ...) it does not actually load the content of that file in to your component like PHP. It simply makes sure that your compiler (probably webpack) knows how to structure the program. It basically creates a reference so webpack knows where to look for functionality.
TL;DR
The import and export here are conceptually different and unrelated things, and both have to be used.
Importing a Vue component is the same with any other importing in JavaScript:
// foo.mjs
export function hello() {
return "hello world!";
}
// bar.mjs
import { hello } from './foo.mjs';
console.log(hello());
Now run node bar.mjs, you will get a feeling how the importing works -- you want to use something that is defined/implemented somewhere else, then you have to import it, regardless of whether it is a Vue component or not.
With regard to export, you are not exporting the components you imported. The only thing you are exporting is the current component. However, this current component may use some other subcomponents in its <template>, so one has to register those subcomponents, by specifying them in the components field in the exported object.
I am trying to create some plugins according to this article:
https://alligator.io/vuejs/creating-custom-plugins/
I have a plugin that needs to run something when the root Vue instance mounts or is created. So far I can only see a way to inject something into all components which is not what I would want.
I simply need to do something when the main Vue instance mounts. How can I do this with a plugin?
The install method from the plugin does not seem to do the trick because this seems to happen before the actual created method.
It's possible to have multiple root Vue components. A "root component" is just a component created with the new syntax and no parent component, so you can detect this as follows:
Vue.mixin({
created() {
if (!this.$parent) {
// This is either the root component or a component
// created with `new` and no parent
}
}
})
It's actually easy to include mixins for just a particular component!
In your component that you want to add the mixin to, just import it like you would anything else, and include an array in your component called mixins like so:
import myMixin from 'src/mixin/myMixin'
export default {
mixins: [myMixin]
}
Then your myMixin code would look like this (don't use Vue.mixin, which is global):
export default {
beforeMount () {
console.log('Your component is about to be mounted!')
}
}