I am following Component Basics guide on vuejs.org, but I cannot produce the result as guided. I don't know whether to put the methods property on component or on root Vue instance.
When I put method onIncreaseCount inside component, an error is thrown.
But when I put method onIncreaseCount inside root Vue instance, although there is no error, nothing is applied when I click the button.
// JS
Vue.component('button-counter', {
data: function(){ return {count: 0} }
template: `<button v-on:click="$emit('increase-count')">You clicked me {{ count }} times.</button>`,
methods: {
onIncreaseCount: function(){ this.count++ }
}
})
new Vue({
el: "#main"
})
// HTML
<main class="main" id="main">
<button-counter title="Example component" #increase-count="onIncreaseCount"></button-counter>
</main>
I expect the {{ count }} value will be increased each time I click the button, but it doesn't change.
you don't need any emit jsut you have to call the increase function
handle in component itself
// JS
Vue.component('button-counter', {
data: function(){ return {count: 0} }
template: `<button v-on:click="increaseCount">You clicked me {{ count }} times.</button>`,
methods: {
increaseCount: function(){ this.count++ }
}
})
new Vue({
el: "#main"
})
// HTML
<main class="main" id="main">
<button-counter title="Example component"></button-counter>
</main>
Related
I have a DefaultLayout component with a dark mode toggle button which is its own component. One if its children (DefaultLayout's) is About.vue where I want a specific image to change its src depending on a localStorage value that can be set to either 'dark' or 'light'.
I've managed to read the localStorage value but the image does not change unless I refresh the page.
I'm new to Vue so I'm lost on how I can create a method to do this in DefaultLayout and change a variable in its child. I've tried to use an emit with no luck.
Could anyone point me in the right direction?
Yes, the local storage is for keeping data not propagate events.
The simplest way for you is to make a prop in child component and pass the value by this prop. But if you want to implement it as global variable the suggested way is by Pinia.
Below is a simple example
Vue.component('About', {
name: 'About',
template: `<div>
<div v-if="mode==='dark'">Dark</div>
<div v-else>Light</div>
</div>
`,
data() {
return {
mode: 'light',
};
},
mounted() {
this.setMode('white'); // In realtime use `this.getMode()` instead of 'white'
},
methods: {
setMode(val) {
this.mode = val;
},
getMode() {
return JSON.parse(localStorage.getItem('mode'));
}
}
});
var app = new Vue({
el: "#app",
template: `<div>
<input type="checkbox" v-model="toggler" #input="setVal" />
<About ref="about" />
</div>`,
data() {
return {
toggler: false,
};
},
methods: {
setVal() {
const mode = this.toggler === false ? 'dark' : 'light';
// localStorage.setItem('mode', mode); // In realtime uncomment this line
this.$refs.about.setMode(mode);
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
</div>
I am using Vue.js 2.
I have a problem with passing value to the child component as a prop. I am trying to pass card to card-component.
In card-component I can access the prop in the Card goes here {{card}} section.
However when I try to access it in created or mounted methods it's undefined.
Parent:
<template>
<div class="container">
<div class="row">
<div class="col-md-8 col-md-offset-2">
<card-component :card="place.card"></card-component>
</div>
</div>
</div>
</template>
<script>
import CostComponent from './CostComponent';
import CardComponent from './CardComponent';
export default {
components: {
CostComponent, CardComponent
},
props: ['id'],
data() {
return {
place: []
}
},
created() {
axios.get('/api/places/' + this.id)
.then(response => this.place = response.data);
}
}
</script>
Child:
<template>
<div class="container">
<div class="row">
<div class="col-md-8 col-md-offset-2">
<ul class="list-unstyled">
Card goes here {{card}}
</ul>
</div>
</div>
</div>
</template>
<script>
import CardItemComponent from './CardItemComponent';
export default {
components: {
CardItemComponent
},
props: ['card'],
created() {
console.log(this.card); // undefined
},
mounted() {
console.log(this.card); // undefined
},
}
</script>
I did a lot of googling but none of the solutions I found have fixed my issue.
This is purely a timing issue. Here's what happens...
Your parent component is created. At this time it has an empty array assigned to place (this is also a problem but I'll get to that later). An async request is started
Your parent component creates a CardComponent instance via its template
<card-component :card="place.card"></card-component>
at this stage, place is still an empty array, therefore place.card is undefined
3. The CardComponent created hook runs, logging undefined
4. The CardComponent is mounted and its mounted hook runs (same logging result as created)
5. Your parent component is mounted
6. At some point after this, the async request resolves and changes place from an empty array to an object, presumably with a card property.
7. The new card property is passed down into your CardComponent and it reactively updates the displayed {{ card }} value in its template.
If you want to catch when the card prop data changes, you can use the beforeUpdate hook
beforeUpdate () {
console.log(this.card)
}
Demo
Vue.component('CardComponent', {
template: '<pre>card = {{ card }}</pre>',
props: ['card'],
created () {
console.log('created:', this.card)
},
mounted () {
console.log('mounted:', this.card)
},
beforeUpdate () {
console.log('beforeUpdate:', this.card)
}
})
new Vue({
el: '#app',
data: {
place: {}
},
created () {
setTimeout(() => {
this.place = { card: 'Ace of Spades' }
}, 2000)
}
})
<script src="https://cdn.jsdelivr.net/npm/vue"></script>
<div id="app">
<card-component :card="place.card" />
</div>
See https://v2.vuejs.org/v2/guide/instance.html#Lifecycle-Diagram
If place is meant to be an object, you should not be initialising it as an array. Also, if your CardComponent relies on data being present, you may want to conditionally render it.
For example
data () {
return { place: null }
}
and
<card-component v-if="place" :card="place.card"></card-component>
then CardComponent will only be created and mounted after place has data.
Make sure you have props: true in the router file. It is a simple solution but many of us forget this.
{
path: '/path-to',
name: 'Name To',
component: Component,
props: true
}
I have a modal in one of my pages and I want to add a class “active” on body when I open the modal, so I can make the body overflow hidden (no scroll).
Is there a way to toogle a class on the body tag when I click from one component? I can't figure it out...
I use routes
<template>
<div id="app">
<Header />
<router-view/>
<Footer />
</div>
</template>
Thx in advance
The correct way of doing this in Vue is to communicate between components, in this case it might not be a simple parent/child communication, so you might want to create an Event Bus.
By using this approach the modal's code is has minimum effects on the rest of your application, it only dispatches events that you can subscribe to from any other component.
Note: In this case you won't add the class on your body tag (because you can't mount Vue on body), but you may just add it to your root div to have a similar result.
const eventBus = new Vue();
Vue.component('modal', {
props: ['isOpen'],
template: `
<div class="modal" v-if="isOpen">This is a modal</div>
`,
});
Vue.component('wrapper', {
template: `
<div>
<modal :isOpen="isModalOpen"></modal>
<button #click="toggleModal">toggle modal</button>
</div>
`,
data() {
return {
isModalOpen: false,
}
},
methods: {
toggleModal() {
this.isModalOpen = !this.isModalOpen;
eventBus.$emit('toggleModal', this.isModalOpen);
}
}
});
new Vue({
el: "#app",
data: {
active: false,
},
created() {
eventBus.$on('toggleModal', (isModalOpen) => {
this.active = isModalOpen;
});
},
})
.active {
background: grey;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.16/vue.min.js"></script>
<div id="app" :class="{active}">
<wrapper></wrapper>
</div>
This should help
document.body.className += 'active'
I'm wanting to change the global variable below throughout the page
Vue.prototype.$color = 'green';
I tried using the code below but it only changes within the component I created
watch: {
cor(newValue, oldVlue) {
this.$color = newValue;
}
}
is it possible for me to create a way to change the prototype variable across all components of the page?
To have $color globally available, you can use a Mixin, more specifically a Global Mixin.
If you would only want it to be read-only, it is simplest solution (less code). See snippet:
Vue.mixin({
created: function () {
this.$color = 'green';
}
})
new Vue({
el: '#app1',
data: {
message: 'Hello Vue.js!'
},
mounted() {
console.log('$color #app1:', this.$color);
}
})
new Vue({
el: '#app2',
data: {
message: 'Hello Vue.js!'
},
mounted() {
console.log('$color #app2:', this.$color);
}
})
<script src="https://unpkg.com/vue#2.5.15/dist/vue.min.js"></script>
<div id="app1">
<p>app1: {{ message }}</p>
</div>
<div id="app2">
<p>app2: {{ message }}</p>
</div>
Making $color reactive
To mave Vue react everywhere to changes to $color, you could use a Vuex store (see other answer).
But if you don't want to use Vuex just for that, another possibility is to create a Vue instance just to hold the "shared" data. After that, create a mixin with a computed property that references the $data of this "shared" Vue instance. See demo below.
// not using a Vuex store, but a separated Vue instance to hold the data
// only use this if you REALLY don't want to use Vuex, because Vuex is preferrable
let globalData = new Vue({
data: { $color: 'green' }
});
Vue.mixin({
computed: {
$color: {
get: function () { return globalData.$data.$color },
set: function (newColor) { globalData.$data.$color = newColor; }
}
}
})
// this.$color will be available in all Vue instances...
new Vue({
el: '#app1'
})
new Vue({
el: '#app2'
})
// ...and components
Vue.component('my-comp', {template: '#t3'});
new Vue({
el: '#app3',
})
<script src="https://unpkg.com/vue#2.5.15/dist/vue.min.js"></script>
<div id="app1">Color: {{ $color }} <button #click="$color = 'red'">change to red</button></div>
<div id="app2">Color: {{ $color }} <button #click="$color = 'yellow'">change to yellow</button></div>
<template id="t3">
<div>Color: {{ $color }} <button #click="$color = 'purple'">change to purple</button></div>
</template>
<div id="app3"><my-comp></my-comp></div>
For completeness, check below to see how using Vuex and Mixin would be (more details on how to use Vuex in the other answer).
// Using a Vuex to hold the "shared" data
// The store is not added to any instance, it is just referenced directly in the mixin
const store = new Vuex.Store({
state: { $color: 'green' },
mutations: { update$color: function(state, newColor) { state.$color = newColor; } }
});
Vue.mixin({
computed: {
$color: {
get: function() { return store.state.$color },
set: function(newColor) { return store.commit('update$color', newColor); }
}
}
})
// this.$color will be available in all Vue instances...
new Vue({
el: '#app1'
})
new Vue({
el: '#app2'
})
// ...and components
Vue.component('my-comp', {template: '#t3'});
new Vue({
el: '#app3',
})
<script src="https://unpkg.com/vue#2.5.15/dist/vue.min.js"></script>
<script src="https://unpkg.com/vuex#3.0.1/dist/vuex.min.js"></script>
<div id="app1">Color: {{ $color }} <button #click="$color = 'red'">change to red</button></div>
<div id="app2">Color: {{ $color }} <button #click="$color = 'yellow'">change to yellow</button></div>
<template id="t3">
<div>Color: {{ $color }} <button #click="$color = 'purple'">change to purple</button></div>
</template>
<div id="app3"><my-comp></my-comp></div>
If you want a reactive global variable, Mixins may not be a good idea. Because even if you are using global Mixins, Vue actually import and inject this Mixin whenever mount new components, which means every time a new variable $color created.
I believe the mutable data types (Object or Array) combined with Vue.prototype can do the trick:
In your main.js file:
Vue.prototype.$color = {value: "black"};
In your *.vue file:
this.$color.value = "red"
In another *.vue file:
console.log(this.$color.value); // "red"
Since you probably want $color to be a property that is not just available, but reactive (and the same) across all components, a possible solution is to use a quick/small Vuex store.
There's a runnable example below. In it you'll see three different Vue instances that will react to the same $color variable (that is at the Vuex store).
All three examples are functionally identical. I wrote them differently just to portrait different ways of using the API. Use what seems more intuitive for you.
const store = new Vuex.Store({
state: {
$color: 'green'
},
mutations: {
update$color: function(state, newColor) { state.$color = newColor; }
}
});
new Vue({
store: store, // add this so the store is available
el: '#app1',
// explicitly via this.$store
computed: {
$color: function() { return this.$store.state.$color }
},
methods: {
update$color: function(newColor) { return this.$store.commit('update$color', newColor); }
}
})
new Vue({
store, // shorthand for store: store
el: '#app2',
// using helpers mapState and mapMutations
computed: {
...Vuex.mapState(['$color'])
},
methods: {
...Vuex.mapMutations(['update$color'])
},
})
new Vue({
store,
el: '#app3',
// using computed properties, only
computed: {
$color: {
get: Vuex.mapState(['$color']).$color,
set: Vuex.mapMutations(['update$color']).update$color
}
},
})
<script src="https://unpkg.com/vue"></script>
<script src="https://unpkg.com/vuex"></script>
<div id="app1">
Color: {{ $color }} <button #click="update$color('blue')">change to blue</button> (explicitly via this.$store)
</div>
<div id="app2">
Color: {{ $color }} <button #click="update$color('red')">change to red</button> (using helpers mapState and mapMutations)
</div>
<div id="app3">
Color: {{ $color }} <button #click="$color = 'orange'">change to orange</button> (using computed properties, only)
</div>
If you want a global reactive variable, you can use this.$root inside child components. There is an example in vuejs docs:
// The root Vue instance
new Vue({
data: {
foo: 1
},
computed: {
bar: function () { /* ... */ }
},
methods: {
baz: function () { /* ... */ }
}
})
// Get root data
this.$root.foo
// Set root data
this.$root.foo = 2
// Access root computed properties
this.$root.bar
// Call root methods
this.$root.baz()
But consider using Vuex in most cases as official docs recommends.
Do this in the component as well
Vue.prototype.$color= 'colorName'
It worked for me.
I'm new using Vue.js and I had a difficulty creating a Button component.
How can I program this component to conditional rendering? In other words, maybe it should be rendering as a router-link maybe as a button? Like that:
<Button type="button" #click="alert('hi!')">It's a button.</Button>
// -> Should return as a <button>.
<Button :to="{ name: 'SomeRoute' }">It's a link.</Button>
// -> Should return as a <router-link>.
You can toggle the tag inside render() or just use <component>.
According to the official specification for Dynamic Components:
You can use the same mount point and dynamically switch between multiple components using the reserved <component> element and dynamically bind to it's is attribute.
Here's an example for your case:
ButtonControl.vue
<template>
<component :is="type" :to="to">
{{ value }}
</component>
</template>
<script>
export default {
computed: {
type () {
if (this.to) {
return 'router-link'
}
return 'button'
}
},
props: {
to: {
required: false
},
value: {
type: String
}
}
}
</script>
Now you can easily use it for a button:
<button-control value="Something"></button-control>
Or a router-link:
<button-control to="/" value="Something"></button-control>
This is an excellent behavior to keep in mind when it's necessary to create elements that may have links or not, such as buttons or cards.
You can create a custom component which can dynamically render as a different tag using the v-if, v-else-if and v-else directives. As long as Vue can tell that the custom component will have a single root element after it has been rendered, it won't complain.
But first off, you shouldn't name a custom component using the name of "built-in or reserved HTML elements", as the Vue warning you'll get will tell you.
It doesn't make sense to me why you want a single component to conditionally render as a <button> or a <router-link> (which itself renders to an <a> element by default). But if you really want to do that, here's an example:
Vue.use(VueRouter);
const router = new VueRouter({
routes: [ { path: '/' } ]
})
Vue.component('linkOrButton', {
template: `
<router-link v-if="type === 'link'" :to="to">I'm a router-link</router-link>
<button v-else-if="type ==='button'">I'm a button</button>
<div v-else>I'm a just a div</div>
`,
props: ['type', 'to']
})
new Vue({ el: '#app', router })
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue-router/3.0.1/vue-router.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.9/vue.js"></script>
<div id="app">
<link-or-button type="link" to="/"></link-or-button>
<link-or-button type="button"></link-or-button>
<link-or-button></link-or-button>
</div>
If you're just trying to render a <router-link> as a <button> instead of an <a>, then you can specify that via the tag prop on the <router-link> itself:
Vue.use(VueRouter);
const router = new VueRouter({
routes: [ { path: '/' } ]
})
new Vue({ el: '#app', router })
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue-router/3.0.1/vue-router.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.9/vue.js"></script>
<div id="app">
<router-link to="/">I'm an a</router-link>
<router-link to="/" tag="button">I'm a button</router-link>
</div>
You can achieve that through render functions.
render: function (h) {
if(this.to){ // i am not sure if presence of to props is your condition
return h(routerLink, { props: { to: this.to } },this.$slots.default)
}
return h('a', this.$slots.default)
}
That should help you start into the right direction
I don't think you'd be able to render a <router-link> or <button> conditionally without having a parent element.
What you can do is decide what to do on click as well as style your element based on the props passed.
template: `<a :class="{btn: !isLink, link: isLink}" #click="handleClick"><slot>Default content</slot></a>`,
props: ['to'],
computed: {
isLink () { return !!this.to }
},
methods: {
handleClick () {
if (this.isLink) {
this.$router.push(this.to)
}
this.$emit('click') // edited this to always emit
}
}
I would follow the advice by #Phil and use v-if but if you'd rather use one component, you can programmatically navigate in your click method.
Your code can look something like this:
<template>
<Button type="button" #click="handleLink">It's a button.</Button>
</template>
<script>
export default {
name: 'my-button',
props: {
routerLink: {
type: Boolean,
default: false
}
},
methods: {
handleLink () {
if (this.routerLink) {
this.$router.push({ name: 'SomeRoute' })
} else {
alert("hi!")
}
}
}
}
</script>