Use Data Variable as Vue Template Without Parent Wrapper - vue.js

I am trying to embed a Codemirror instance as a Vue component, similar to what was accomplished in this project. However, instead of returning a template of the Codemirror instance inside of a parent
<div class="vue-codemirror" :class="{ merge }">
<!-- Textarea will be replaced by Codemirror instance. -->
<textarea ref="textarea" :name="name" :placeholder="placeholder" v-else>
</textarea>
</div>
I am simplying trying to return the Codemirror instance alone. The reason why I can't simply remove the parent div and have
<!-- Textarea will be replaced by Codemirror instance. -->
<textarea ref="textarea" :name="name" :placeholder="placeholder" v-else>
</textarea>
is because the method to replace the textarea, CodeMirror.fromTextArea(), requires the textarea to have a parentNode. Otherwise, a null error will be encountered.
Luckily, there is a way to create a Codemirror instance without using a textarea at all, CodeMirror(). This instance has a function getWrapperElement() that returns the DOM node:
<div class="CodeMirror cm-s-default">
...
</div>
I want to output this specific DOM node relating to Codemirror instance using the Vue template/render function. The current way I'm creating the instance is by initializing it in the component data object.
data: function () {
// Create a CodeMirror instance.
let cm = new CodeMirror(null, {
...
})
return {
// Define a CodeMirror instance for each CodeBlockView.
cm : cm,
...
}
},
Update 1: I have found one way to do this, albeit very hacker-ish. We use the createElement function that is passed in with render and pass into the data object argument the innerHTML of DOM node we want to render. It seems to be working visually but the CodeMirror instance isn't editable.
render: function (createElement) {
return createElement('div', {
class: this.dom.classList.value,
domProps: {innerHTML: this.dom.innerHTML}
})
}
Update 2: However, this doesn't pass in the actual DOM node rather it only shallowly copies it; this presents a problem as it doesn't allow it to be editable nor have a CodeMirror instance attached.

You cannot change the template anymore after the component has been created. It's not a property of the component but a parameter that is passed to the constructor as far as I know.
Hence, you would need to create the CodeMirror instance before the component is created and inject it.
However, I fail to see the problem with a wrapping component, could you explain the why?

I test many ways and the most simple template I find was keeping the textarea, after that the component should receive options and value and emit the new value.
you can test the component here
I'm not a codeMirror expert, I import many things for keep the codemirror component more flexible, you can adjust the imports with your needs.
//component codeMirror.vue
<template>
<textarea ref="myCm"></textarea>
</template>
<script>
import CodeMirror from 'codemirror';
// language
import 'codemirror/mode/javascript/javascript';
// theme css
import 'codemirror/lib/codemirror.css';
import 'codemirror/theme/monokai.css';
// require active-line.js
import 'codemirror/addon/selection/active-line';
// styleSelectedText
import 'codemirror/addon/selection/mark-selection';
import 'codemirror/addon/search/searchcursor';
// hint
import 'codemirror/addon/hint/show-hint';
import 'codemirror/addon/hint/show-hint.css';
import 'codemirror/addon/hint/javascript-hint';
// highlightSelectionMatches
import 'codemirror/addon/scroll/annotatescrollbar';
import 'codemirror/addon/search/matchesonscrollbar';
import 'codemirror/addon/search/match-highlighter';
// keyMap
import 'codemirror/mode/clike/clike';
import 'codemirror/addon/edit/matchbrackets';
import 'codemirror/addon/comment/comment';
import 'codemirror/addon/dialog/dialog';
import 'codemirror/addon/dialog/dialog.css';
import 'codemirror/addon/search/search';
import 'codemirror/keymap/sublime';
// foldGutter
import 'codemirror/addon/fold/foldgutter.css';
import 'codemirror/addon/fold/brace-fold';
import 'codemirror/addon/fold/comment-fold';
import 'codemirror/addon/fold/foldcode';
import 'codemirror/addon/fold/foldgutter';
import 'codemirror/addon/fold/indent-fold';
import 'codemirror/addon/fold/markdown-fold';
import 'codemirror/addon/fold/xml-fold';
export default {
name: 'codeMirror',
props: {
value: String, // give to the component a start value
options: Object, // give the codeMirror options
},
mounted() {
const myCodemirror = new CodeMirror.fromTextArea(this.$refs.myCm, this.options);
myCodemirror.setValue(this.value);
myCodemirror.on('change', (cm) => {
if (this.$emit) {
this.$emit('input', cm.getValue());
}
});
},
};
</script>
after that is easy to use this component for render codeMirror in multiple instances, readOnly, recovery de data, multiple templates, no limits. ex:
<template>
<div>
Read Only, default theme, value multiple line
<codeMirror :value="value0" :options="noChanges"></codeMirror>
Value Dynamic, theme monokai, other extra fancy things
<codeMirror :value="value" :options="monokai" #input="onCmCodeChange"></codeMirror>
Only for debug, shows the modifications made inside codemirror
{{ value }}
</div>
</template>
<script>
// # is an alias to /src
import codeMirror from '#/components/codeMirror.vue';
export default {
name: 'pageEditor',
components: {
codeMirror,
},
data() {
return {
value0: `let choco: "bombon";
let type: 'caramel;
choco + ' ' + type;`,
value: 'let frankie= "It\'s alive"',
noChanges: {
theme: 'default',
readOnly: true,
tabSize: 2,
line: true,
lineNumbers: true,
},
monokai: {
tabSize: 2,
styleActiveLine: true,
lineNumbers: true,
line: true,
foldGutter: true,
styleSelectedText: true,
mode: 'text/javascript',
keyMap: 'sublime',
matchBrackets: true,
showCursorWhenSelecting: true,
theme: 'monokai',
extraKeys: { Ctrl: 'autocomplete' },
hintOptions: {
completeSingle: false,
},
},
};
},
methods: {
onCmCodeChange(newValue) {
this.value = newValue;
},
},
};
</script>
I hope this help

Related

What's the most idomatic Vue way of handling this higher-order component?

I have a VueJS organization and architecture question. I have a bunch of pages that serve as CRUD pages for individual objects in my system. They share a lot of code . I've abstracted this away in a shared component but I don't love what I did and I'm looking for advice on the idiomatic Vue way to do this.
I'm trying to create a higher order component that accepts two arguments:
An edit component that is the editable view of each object. So you can think of it as a stand in for a text input with a v-model accept that it has tons of different inputs.
A list component which displays a list of all the objects for that type in the system. It controls navigation to edit that object.
Normally this would be simply something where I use slots and invoke this component in the view page for each CRUD object. So basically I'd have something like this:
<!-- this file is src/views/DogsCRUDPage.vue -->
<template>
<general-crud-component
name="dogs"
backendurl="/dogs/"
>
<template slot="list">
<dogs-list-component />
</template>
<template slot="edit">
<dogs-edit-field v-model="... oops .." />
</template>
</general-crud-component>
</template>
<script>
export default {
name: "DogCRUDPage",
components: {
GeneralCrudComponent,
DogListComponent,
DogEditField,
},
}
</script>
This is nice because it matches the general syntax of all of my other VueJS pages and how I pass props and things to shared code. However, the problem is that GeneralCRUDComponent handles all of the mechanisms for checking if an object is edited, and therefor hiding or unhiding the save button, etc. Therefor it has the editable object in its data which will become the v-model for DogsEditField or any other that's passed to it. So it needs to pass this component a prop. So what I've done this:
// This file is src/utils/crud.js
import Vue from "vue"
const crudView = (listComponent, editComponent) => {
return Vue.component('CrudView', {
template: `
<v-row>
<list-component />
<v-form>
<edit-component v-model="obj" />
</v-form>
</v-row>
`,
components: {
ListComponent: listComponent,
EditComponent: editComponent,
},
data() {
return {
obj: {},
}
},
})
}
export default crudView
This file has a ton of shared code not shown that is doing the nuts and bolts of editing, undo, saving, etc.
And then in my src/router/index.js
//import DogCRUDPage from "#/views/libs/DogCRUDPage"
import crudView from "#/utils/crud"
import DogListComponent from "#/components/DogListComponent"
import DogEditField from "#/components/design/DogEditField"
const DogCRUDPage = crudView(DesignBasisList, DesignBasis)
Vue.use(VueRouter);
export default new VueRouter({
routes: [
{
path: "/dog",
name: "dog",
component: DogCRUDPage,
},
})
This is working, but there are issues I don't love about it. For one, I needed to enable runtimecompiler for my project which increases the size of the payload to the browser. I need to import the list and edit components to my router instead of just the page for every single object I have a page for. The syntax for this new shared component is totally different from the template syntax all the other pages use. It puts all of my page creation into the router/index.js file instead of just layed out as files in src/views which I am used to in Vue.
What is the idiomatic way to accomplish this? Am I on the right track here? I'm happy to do this, it's working, if this really is how we do this in Vue. But I would love to explore alternatives if the Vue community does something differently. I guess I'm mostly looking for the idiomatic Vue way to accomplish this. Thanks a bunch.
How about this:
DogsPage.vue
<template>
<CrudView
:editComponent="DogsEdit"
:listComponent="DogsList"
></CrudView>
</template>
<script>
import DogsEdit from '#/components/DogsEdit.vue'
import DogsList from '#/components/DogsList.vue'
import CrudView from '#/components/CrudView.vue'
export default {
components: { CrudView },
data() {
return { DogsEdit, DogsList }
}
}
</script>
CrudView.vue
<template>
<div>
<component :is="listComponent"></component>
<component :is="editComponent" v-model="obj"></component>
</div>
</template>
<script>
export default {
props: {
editComponent: Object,
listComponent: Object
},
data() {
return {
obj: {}
}
}
}
</script>

Passing props to Vue root instance via attributes on element the app is mounted on

I am terribly new to Vue, so forgive me if my terminology is off. I have a .NET Core MVC project with small, separate vue pages. On my current page, I return a view from the controller that just has:
#model long;
<div id="faq-category" v-bind:faqCategoryId="#Model"></div>
#section Scripts {
<script src="~/scripts/js/faqCategory.js"></script>
}
Where I send in the id of the item this page will go grab and create the edit form for. faqCategory.js is the compiled vue app. I need to pass in the long parameter to the vue app on initialization, so it can go fetch the full object. I mount it with a main.ts like:
import { createApp } from 'vue'
import FaqCategoryPage from './FaqCategoryPage.vue'
createApp(FaqCategoryPage)
.mount('#faq-category');
How can I get my faqCategoryId into my vue app to kick off the initialization and load the object? My v-bind attempt seems to not work - I have a #Prop(Number) readonly faqCategoryId: number = 0; on the vue component, but it is always 0.
My FaqCategoryPAge.vue script is simply:
<script lang="ts">
import { Options, Vue } from "vue-class-component";
import { Prop } from 'vue-property-decorator'
import Card from "#/Card.vue";
import axios from "axios";
import FaqCategory from "../shared/FaqCategory";
#Options({
components: {
Card,
},
})
export default class FaqCategoryPage extends Vue {
#Prop(Number) readonly faqCategoryId: number = 0;
mounted() {
console.log(this.faqCategoryId);
}
}
</script>
It seems passing props to root instance vie attributes placed on element the app is mounting on is not supported
You can solve it using data- attributes easily
Vue 2
const mountEl = document.querySelector("#app");
new Vue({
propsData: { ...mountEl.dataset },
props: ["message"]
}).$mount("#app");
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app" data-message="Hello from HTML">
{{ message }}
</div>
Vue 3
const mountEl = document.querySelector("#app");
Vue.createApp({
props: ["message"]
}, { ...mountEl.dataset }).mount("#app");
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/3.0.0/vue.global.js"></script>
<div id="app" data-message="Hello from HTML">
{{ message }}
</div>
Biggest disadvantage of this is that everything taken from data- attributes is a string so if your component expects something else (Number, Boolean etc) you need to make conversion yourself.
One more option of course is pushing your component one level down. As long as you use v-bind (:counter), proper JS type is passed into the component:
Vue.createApp({
components: {
MyComponent: {
props: {
message: String,
counter: Number
},
template: '<div> {{ message }} (counter: {{ counter }}) </div>'
}
},
}).mount("#app");
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/3.0.0/vue.global.js"></script>
<div id="app">
<my-component :message="'Hello from HTML'" :counter="10" />
</div>
Just an idea (not a real problem)
Not really sure but it can be a problem with Props casing
HTML attribute names are case-insensitive, so browsers will interpret any uppercase characters as lowercase. That means when you're using in-DOM templates, camelCased prop names need to use their kebab-cased (hyphen-delimited) equivalents
Try to change your MVC view into this:
<div id="faq-category" v-bind:faq-category-id="#Model"></div>
Further to Michal LevĂ˝'s answer regarding Vue 3, you can also implement that pattern with a Single File Component:
app.html
<div id="app" data-message="My Message"/>
app.js
import { createApp } from 'vue';
import MyComponent from './my-component.vue';
const mountEl = document.querySelector("#app");
Vue.createApp(MyComponent, { ...mountEl.dataset }).mount("#app");
my-component.vue
<template>
{{ message }}
</template>
<script>
export default {
props: {
message: String
}
};
</script>
Or you could even grab data from anywhere on the parent HTML page, eg:
app.html
<h1>My Message</h1>
<div id="app"/>
app.js
import { createApp } from 'vue';
import MyComponent from './my-component.vue';
const message = document.querySelector('h1').innerText;
Vue.createApp(MyComponent, { message }).mount("#app");
my-component.vue
<template>
{{ message }}
</template>
<script>
export default {
props: {
message: String
}
};
</script>
To answer TheStoryCoder's question: you would need to use a data prop. My answers above demonstrate how to pass a value from the parent DOM to the Vue app when it is mounted. If you wanted to then change the value of message after it was mounted, you would need to do something like this (I've called the data prop myMessage for clarity, but you could also just use the same prop name message):
<template>
{{ myMessage }}
<button #click="myMessage = 'foo'">Foo me</button>
</template>
<script>
export default {
props: {
message: String
},
data() {
return {
myMessage: this.message
}
}
};
</script>
So I'm not at all familiar with .NET and what model does, but Vue will treat the DOM element as a placeholder only and it does not extend to it the same functionality as the components within the app have.
so v-bind is not going to work, even without the value being reactive, the option is not there to do it.
you could try a hack to access the value and assign to a data such as...
const app = Vue.createApp({
data(){
return {
faqCategoryId: null
}
},
mounted() {
const props = ["faqCategoryId"]
const el = this.$el.parentElement;
props.forEach((key) => {
const val = el.getAttribute(key);
if(val !== null) this[key] = (val);
})
}
})
app.mount('#app')
<script src="https://unpkg.com/vue#3.0.0-rc.11/dist/vue.global.prod.js"></script>
<div id="app" faqCategoryId="12">
<h1>Faq Category Id: {{faqCategoryId}}</h1>
</div>
where you get the value from the html dom element, and assign to a data. The reason I'm suggesting data instead of props is that props are setup to be write only, so you wouldn't be able to override them, so instead I've used a variable props to define the props to look for in the dom element.
Another option
is to use inject/provide
it's easier to just use js to provide the variable, but assuming you want to use this in an mvc framework, so that it is managed through the view only. In addition, you can make it simpler by picking the exact attributes you want to pass to the application, but this provides a better "framework" for reuse.
const mount = ($el) => {
const app = Vue.createApp({
inject: {
faqCategoryId: {
default: 'optional'
},
},
})
const el = document.querySelector($el)
Object.keys(app._component.inject).forEach(key => {
if (el.getAttribute(key) !== null) {
app.provide(key, el.getAttribute(key))
}
})
app.mount('#app')
}
mount('#app')
<script src="https://unpkg.com/vue#3.0.0-rc.11/dist/vue.global.prod.js"></script>
<div id="app" faqCategoryId="66">
<h1>Faq Category Id: {{faqCategoryId}}</h1>
</div>
As i tried in the following example
https://codepen.io/boussadjra/pen/vYGvXvq
you could do :
mounted() {
console.log(this.$el.parentElement.getAttribute("faqCategoryId"));
}
All other answers might be valid, but for Vue 3 the simple way is here:
import {createApp} from 'vue'
import rootComponent from './app.vue'
let rootProps = {};
createApp(rootComponent, rootProps)
.mount('#somewhere')

Vue - How to pass and use dynamically multiple components as props

I'm using AgGrid as the grid to show the data in the site.
Following this example Example: Rendering using VueJS Components, I'm able to use different components to be rendered into different columns.
Now that I need to implement this grid in multiple views, I want to make a "custom component" that implements the ag-grid-vue component, and receives just the column definitions, row data and components (if the columns are rendering another component).
Something like this:
<template>
<div>
<ag-grid-vue
:animateRows="true"
:columnDefs="columnDefs"
:frameworkComponents="frameworkComponents"
:defaultColDef="defaultColDef"
:gridOptions="gridOptions"
:pagination="true"
:paginationPageSize="paginationPageSize"
:rowData="rowData"
:suppressPaginationPanel="true"
colResizeDefault="shift"
ref="agGridTable"
rowSelection="multiple"
></ag-grid-vue>
</div>
</template>
<script>
import { AgGridVue } from "ag-grid-vue";
export default {
name: "AgGrid",
components: { AgGridVue },
props: ['columnDefs', 'components', 'rowData'],
data() {
return {
gridApi: null,
gridOptions: {},
defaultColDef: {
sortable: true,
resizable: true,
suppressMenu: true
},
frameworkComponents: null
}
},
beforeMount() {
this.frameworkComponents = this.components;
}
}
</script>
Now the parent will pass all the data needed:
<ag-grid :column-defs="columnDefs" :components="frameworkComponents" :row-data="gridList"></ag-grid>
The problem comes when I try to pass these components as props:
this.frameworkComponents = {
squareRenderer: SquareRenderer,
cubeRenderer: CubeRenderer,
paramsRenderer: ParamsRenderer,
currencyRenderer: CurrencyRenderer,
childMessageRenderer: ChildMessageRenderer,
};
Obviously, my custom component doesn't know these components because they are not imported, so the view could not find those components. Since each view will display diferent columns, and these one could or not display renderer components, I need to pass all the components needed to the grid component and import them.
Any ideas how to import and use those components?

retrieve content from markdown file and convert it to valid HTML code in vuejs

I want to create a documentation page and have some markdown files which represent the main content. I have a navigation sidebar where I can select the specific content.
When clicking on a navigation item I need to read the content from a markdown file. I have a method that returns me the required path but I don't know how to read the file.
Lastly I took marked to render the markdown syntax to HTML code.
I created a small example that shows what is missing
https://codesandbox.io/s/006p3m1p1l
Is there something I can use to read the markdown content?
Use VueResource to retrieve the content from your markdown file.
Import the VueResource, and add it using Vue.use method (main.js):
import Vue from "vue";
import App from "./App";
import VueResource from "vue-resource";
Vue.config.productionTip = false;
Vue.use(VueResource);
new Vue({
el: "#app",
components: { App },
template: "<App/>"
});
Then use this.$http.get() method it within your App.vue file to retrieve the markdown file conent.
You can use markdown parsing library, like Showdown.js, wrapped within a vue.js method, directive or filter.
See: https://github.com/showdownjs/showdown and http://showdownjs.com/
There is also vuejs component wrapper for Showdown:
See: https://github.com/meteorlxy/vue-showdown and https://vue-showdown.js.org/
In your case that should look something like this ( using vue-showdown):
<template>
<div id="app"><VueShowdown :markdown="fileContent"></VueShowdown></div>
</template>
<script>
import VueShowdown from "vue-showdown";
export default {
name: "App",
components: VueShowdown,
data: function() {
return {
fileContent: null,
fileToRender:
"https://gist.githubusercontent.com/rt2zz/e0a1d6ab2682d2c47746950b84c0b6ee/raw/83b8b4814c3417111b9b9bef86a552608506603e/markdown-sample.md",
rawContent: null
};
},
created: function() {
// const fileToRender = `./assets/documentation/general/welcome.md`;
//const rawContent = ""; // Read the file content using fileToRender
// this.fileContent = "### marked(rawContent) should get executed";
this.getContent();
},
methods: {
getContent() {
this.fileContent = "rendering ";
// var self;
this.$http.get(this.fileToRender).then(
response => {
// get body data
this.fileContent = response.body;
},
response => {
// error callback
this.fileContent = "An error ocurred";
}
);
}
}
};
</script>
Check in sandbox: https://codesandbox.io/s/poknq9z6q
If your markdown file load is one time thing, then you could import it data, just like you import the components, js files and libraries:
<template>
<div id="app"><VueShowdown :markdown="fileContent"></VueShowdown></div>
</template>
<script>
import VueShowdown from "vue-showdown";
import MarkDownData from './assets/documentation/general/welcome.md';
export default {
name: "App",
components: VueShowdown,
data: function() {
return {
fileContent: null,
rawContent: null
};
},
created: function() {
// const fileToRender = `./assets/documentation/general/welcome.md`;
//const rawContent = ""; // Read the file content using fileToRender
// this.fileContent = "### marked(rawContent) should get executed";
this.getContent();
},
methods: {
getContent() {
this.fileContent = MarkDownData;
}
}
};
</script>
See: https://codesandbox.io/s/xpmy7pzyqz
You could also do it with a combination of html-loader, markdown-loader & v-html.
First you need to install the loaders:
npm i html-loader markdown-loader
Then declare a computed property that returns an array with the names of the markdown files.
In data - add showContent and set the wanted default value - the init markdown file that gets loaded.
Then in the template - loop through the array and set the wanted markdown file on click.
Then finally, you can load your markdown files with a combination of v-html and template literals.
Example below:
<template>
<div class="home">
<h1>
Markdown files
</h1>
<ul>
<li
v-for="item in docs"
:key="item"
#click="shownContent = item"
>
{{ item }}
</li>
</ul>
<div v-html="require(`!!html-loader!markdown-loader!../assets/docs/${shownContent}.md`)"></div>
</div>
</template>
<script>
export default {
name: 'Home',
data() {
return {
shownContent: 'doc1',
}
},
computed: {
docs() {
return [
'doc1',
'doc2',
'doc3',
]
},
},
}
</script>
This way it's important to note, that the name in the array has to be the same as the markdownfile.
I followed the example as mentioned above. I put the code in a component, not App.vue
https://codesandbox.io/s/xpmy7pzyqz?file=/src/App.vue
I get the following error
[Vue warn]: Invalid prop: type check failed for prop "markdown". Expected String with value "[object Object]", got Object

Determining if slot content is null or empty

I have a little Loading component, whose default text I want to be 'Loading...'. Good candidate for slots, so I have something like this as my template:
<p class="loading"><i class="fa fa-spinner fa-spin"></i><slot>Loading...</slot></p>
That allows me to change the loading message with e.g. <loading>Searching...</loading>. The behaviour I would like, though, is not just to display the default message if no slot content is supplied, but also if the slot content is null or blank. At the moment if I do e.g.<loading>{{loadingMessage}}</loading> and loadingMessage is null, no text is displayed (where I want the default text to be displayed). So ideally I need to test this.$slots.default. This tells me whether content was passed in, but how do I find whether or not it was empty? this.$slots.default.text returns undefined.
You'd need a computed property which checks for this.$slots. With a default slot you'd check this.$slots.default, and with a named slot just replace default with the slot name.
computed: {
slotPassed() {
return !!this.$slots.default[0].text.length
}
}
And then use it in your template:
<template>
<div>
<slot v-if="slotPassed">Loading...</slot>
<p v-else>Searching...</p>
</div>
</template>
You can see a small example here. Notice how fallback content is displayed and not "default content", which is inside the slot.
Edit:
My wording could've been better. What you need to do is check for $slots.X value, but computed property is a way to check that. You could also just write the slot check in your template:
<template>
<div>
<slot v-if="!!$slots.default[0].text">Loading...</slot>
<p v-else>Searching...</p>
</div>
</template>
Edit 2: As pointed out by #GoogleMac in the comments, checking for a slot's text property fails for renderless components (e.g. <transition>, <keep-alive>, ...), so the check they suggested is:
!!this.$slots.default && !!this.$slots.default[0]
// or..
!!(this.$slots.default || [])[0]
#kano's answer works well, but there's a gotcha: this.$slots isn't reactive, so if it starts out being false, and then becomes true, any computed property won't update.
The solution is to not rely on a computed value but instead on created and beforeUpdated (as #MathewSonke points out):
export default {
name: "YourComponentWithDynamicSlot",
data() {
return {
showFooter: false,
showHeader: false,
};
},
created() {
this.setShowSlots();
},
beforeUpdate() {
this.setShowSlots();
},
methods: {
setShowSlots() {
this.showFooter = this.$slots.footer?.[0];
this.showHeader = this.$slots.header?.[0];
},
},
};
UPDATE: Vue 3 (Composition API)
For Vue 3, it seems that the way to check whether a slot has content has changed (using the new composition API):
import { computed, defineComponent } from "vue";
export default defineComponent({
setup(_, { slots }) {
const showHeader = computed(() => !!slots.header);
return {
showHeader,
};
},
});
note: I can't find any documentation on this, so take it with a pinch of salt, but seems to work in my very limited testing.
this.$slots can be checked to see if a slot has been used.
It is important to note that this.$slots is not reactive. This could cause problems when using this.$slots in a computed value.
https://v2.vuejs.org/v2/api/?redirect=true#:~:text=Please%20note%20that%20slots%20are%20not%20reactive.
This means we need to ensure that this.slots is checked whenever the component re-renders. We can do this simply by using a method instead of a computed property.
https://v2.vuejs.org/v2/guide/computed.html?redirect=true#:~:text=In%20comparison%2C%20a%20method%20invocation%20will%20always%20run%20the%20function%20whenever%20a%20re%2Drender%20happens
<template>
<div>
<slot v-if="hasHeading" name="heading"/>
</div>
</template>
<script>
export default{
name: "some component",
methods: {
hasHeading(){ return !!this.slots.heading}
}
}
</script>