The guide is quite confusing and obviously not correct when trying to set up Cypress 10 for component testing with Vue2 and Vuetify with composition API. There's lots of errors of unknown tags, things returned from setup() aren't accessible, spread operators where there shouldn't be, imports that don't work etc. What's the correct way to set things up so testing works?
You need to set up Vuetify as regular, to the global Vue object. Then in the mount you need to give the Vuetify object to the mount function so it can be found by the components. When using Composition API that also needs to be set up regularly to the global instance (unlike Vuetify it also works in the local instance, if you want).
Then mount the component inside a v-appso it should work properly and pass arugments around.
So component.ts file will include this:
import { mount } from 'cypress/vue2'
import Vuetify from 'vuetify'
import VueCompositionAPI from '#vue/composition-api';
import Vue from 'vue'
import { VApp } from 'vuetify/lib/components/VApp';
Vue.use(Vuetify);
Vue.use(VueCompositionAPI);
Cypress.Commands.add('mount', (component, args) => {
args.vuetify = new Vuetify(yourVuetifyOptions);
return mount({ render: (h) => h(VApp, [h(component, args)]) }, args);
})
When using the mount just do:
cy.mount(myComponent, { props: {someProp: 123 } });
If you need to set up plugins for the local Vue instance in the test they need to be set in args.extensions.plugins, the guide seems to mention globals but that is incorrect.
cy.mount(myComponent, { props: {someProp: 123 }, extensions: { plugins: [MyPlugin] } });
Note that I'm using args for both settings parameters for mount and also for the component, if needed those two can be separated. But there shouldn't be much clashing of properties and attributes so this works.
Also the props/attributes/etc for the component must be given as they're given to createElement, not mount (so props instead of propsData etc).
My main.js contains import "mathjs"; and seems to be working fine within main.js as
console.log(median(5,4,6,1));
> 4.5
median() is however not available outside of main.js, i.e. in components. After reading this answer, I assumed that the simple import should be enough for global availability throughout the vue app?
In general when you are working with modern modules or a bundler like webpack, you have to import mathjs in every module (think file) you want to use it.
What is often done in the vue context, is adding the library to the Vue context itself with a plugin.
See https://v3.vuejs.org/guide/plugins.html#writing-a-plugin
So this should be as easy as:
const mathjsPlugin = {
install(app){
app.config.globalProperties.$mathjs = mathjs;
}
}
const app = createApp(...);
app.use(mathjsPlugin);
// inside of a component
export default {
created(){
console.log(this.$mathjs....);
}
}
I personally think explicitly importing is a cleaner approach, but if mathjs is used in most of the components, this approach can make sense
in main.js import all as math then add it as global property :
import * as math from 'mathjs'
const app=createApp({....})
app.config.globalProperties.$math =math
then in any component you could use it like this.$math.theFunctionName
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!')
}
}
This is Vue.js question, generally I'm trying to use 'scrollMonitor' function inside of my .vue instance(imported via main.js) but it gives me a typical 'this.scrollMonitor is not a function' error
mounted () {
let watcher = this.$scrollMonitor(this.$refs.nicer)
}
In main.js ScrollMonitor library seems to be properly imported(console shows what's expected):
import scrollMonitor from 'scrollmonitor'
Vue.use(scrollMonitor)
console.log(scrollMonitor)
Again main goal is using scrollMonitor functionality inside of .vue file(in vue component instance). Sorry if I'm missing something silly here - I'm already using some other libraries like Vue-Resource in that file so issue is not in 'filepath' but rather in the way I'm using scrollMonitor functionality, any help is much appreciated, thank you !
For those who are still looking: there is a way of adding plain js libraries to the main.js and then using them with ease globally in inner components(this is not about mixins):
import scrollmonitor from 'scrollmonitor'
Object.defineProperty(Vue.prototype, '$scrollmonitor', {
get() {return this.$root.scrollmonitor}
})
also it should be added to main Vue data object:
data () {
return { scrollmonitor }
},
And then it can be used within mounted() callback (not created() one) inside of the component itself, with scrollmonitor it may look like this(in my specific case the template had a div with ref="nicer" attribute, 'create' is a method specific to the library api):
mounted () {
this.$scrollmonitor.create(this.$refs.nicer)
}
Hooray, I hope someone may find this useful as I did!
Are you using a plain javascript library and trying to Vue.use it? That won't really work. Vue.use will only work with plugins designed to work with Vue. Import the library into the component that needs and and just use it there.
scrollMonitor(this.$refs.nicer)