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after changing vuejs's html heading by calling this.$refs, vuejs not updating that html element afterwards

i have simple html code :
<script src="vue.js"></script>
<div id="app1">
<h1 ref="heading">{{ title }}</h1>
<button v-on:click="change" ref="myButton">Change Title</button>
</div>
<script src="app.js"></script>
and this is app.js
let v1=new Vue({
el: '#app1',
data: {
title: 'The VueJS Instance'
},
methods: {
change: function() {
this.title ='The VueJS Instance (Updated)';
}
},
watch: {
title: function(value) {
alert('Title changed, new value: ' + value);
}
}
});
v1.$refs.heading.innerText="BEFORE Change";
As you can see i am setting innertext for "h1 heading" element. After that i am clicking on button which will call change method, after that call it opens a new dialog window saying "Title changed, new value: The VueJS Instance (Updated)" but the page (h1 heading) not updated it still remains same "BEFORE Change", What is wrong in my code, i think it should update the heading (i am using Vue.js v2.6.11 version). Thanks

You should never update the DOM of a Vue template directly - otherwise the synchronization between the virtual DOM and the real DOM will be lost and you will get all kinds of strange errors or awkward behavior.
Noone can save you from shooting yourself in the foot. Remove the last statement in your code and you will see that the title is properly updated.

Vue.js mount component after DOM tree mutation to add a vue component

I have a use case (below) where I need to mount (if thats the correct term) a Vue.js component template that was inserted into the DOM via jQuery, I can setup a Mutation Observer or react to certain events that are triggered when the mutation happens.
I am using Vue.js v2
Here is a simple example I put together to illustrate the point:
live jsFiddle https://jsfiddle.net/w7q7b1bh/2/
The HTML below contains inlined-templates for two components
<script src="https://cdn.jsdelivr.net/npm/vue#2.5.13/dist/vue.min.js"></script>
<script src="https://code.jquery.com/jquery-3.3.1.min.js"></script>
<div id="app">
<!-- The use of inline-template is required for my solution to work -->
<simple-counter inline-template>
<button v-bind:style="style" v-on:click="add">clicks: {{ counter }}</button>
</simple-counter>
<simple-counter inline-template>
<button v-on:click="counter += 1">{{ counter }}</button>
</simple-counter>
</div>
<button id="mutate">Mutate</button>
The js:
// simple counter component
Vue.component('simple-counter', {
data: function() {
return {
counter: 0,
style: {
color: 'red',
width: '200px'
}
}
},
methods: {
add: function() {
this.counter = this.counter + 1;
this.style.color = this.style.color == 'red' ? 'green' : 'red';
}
}
})
// create the Vue instance
var initV = () => new Vue({
el: '#app'
});
// expose the instance for later use
window.v = initV();
// click handler that will add a new `simple-counter` template to the Vue.el scope
$('#mutate').click(function(){
$('#app').append(` <div is="simple-counter" inline-template>
<button v-bind:style="style" v-on:click="add">click to add: <span class="inactive" v-bind:class="{ active: true }">{{ counter }}</span></button></div>`)
// do something after the template is incerted
window.v.$destroy()
window.v = initV(); // does not work
})
As mentioned in the code, destroying the re-instantiating the Vue instance does not work, I understand why, the templates for the components are changed on first Vue instantiation to their final HTML, when you try and instantiate a second time, templates are not there, components are not mounted
I'd like to be able to find the newly added components after mutation and mount only those, is that possible? and how?
UPDATE:
I was able to find a way to do it via instantiating a new Vue instance with el set to the specific mutated part of the DOM as opposed to the whole #app tree:
$('#mutate').click(function(){
var appended =
$(`
<div is="simple-counter" inline-template>
<button v-bind:style="style" v-on:click="add">
click to add: {{ counter }}
</button>
</div>`
).appendTo($('#app'));
var newV = new Vue({el: appended[0]});
});
Seems to work, but also looks ugly and I am not sure what other implications this might have..
Use Case:
I am working on a way to write Vue.js components for a CMS called Adobe Experience Manager (AEM).
I write my components using inlined-template which gives me the advantage of SEO as well as server-side rendering using another templating language called HTL.
The way AEM authoring works is that, when a component is edited (via a dialog), that specific component is re-rendered on the server-side then injected back to the DOM to replace the old component, all done via Ajax and jQuery (no browser refresh).
Here is an example
AEM component template:
<button>${properties.buttonTitle}</button>
Here is what an author might do:
author visits the authoring page
opens the button component dialog to edit
changes the buttonTitle to "new button title"
Saves
upon saving, an ajax is sent, the component HTML is re-rendered on the server and returned is the new HTML. That HTML now replaces the old HTML via jQuery (mutates the DOM)
This is fine for static components, but if this was a Vue.js component, how do I dynamically mount it while keeping other components mounted.
An easy solution to this is to refresh the page... but that is just bad experience... There has to be a better way.

Thanks to #liam I was able to find an appropriate solution to my problem
After mutating the DOM with the HTML template, keep a reference to that template's parent element
for example:
var $template = $('<div is="simple-counter" inline-template> ..rest of template here.. <div>').appendTo('#app') // app is the Vue instance el or a child of it
Now you can create a new instance of your component and add $template to it as the el property
if my component was:
var simpleCounterComponent = Vue.component('simple-counter', {
data: function() {
return {
counter: 0,
style: {
color: 'red',
width: '200px'
}
}
},
methods: {
add: function() {
this.counter = this.counter + 1;
this.style.color = this.style.color == 'red' ? 'green' : 'red';
}
}
})
I can do:
var instance = new simpleCounterComponent({
el: $template.get(0) // getting an HTML element not a jQuery object
});
And this way, that newly added template has become a Vue component
Take a look at this fiddle for working example based on the question:
https://jsfiddle.net/947ojvnw/11/

One way to instantiate Vue components in runtime-generated HTML is:
var ComponentClass = Vue.extend({
template: '...',
});
var instance = new ComponentClass({
propsData: { name: value },
});
instance.$mount('#uid'); // HTML contains <... id="uid">
...
instance.$destroy(); // if HTML containing id="uid" is dropped
More here (I am not affiliated with this site)
https://css-tricks.com/creating-vue-js-component-instances-programmatically/

How to control order of rendering in vue.js for sibling component

I have following kind of code:
<div>
<compA />
<compB />
</div>
How do I make sure that first compA is rendered only after it compB is rendered.
Why I want is I have some dependency on few elements of compA, and style of compB depends on presence of those elements.
Why in details:
I have some complex UI design, where one box will become fixed when you scroll. SO It will not go above the screen when you scroll, it will be fixed once you start scrolling and it start touching the header. So I am using jquery-visible to find if a div with a particular id is visible on the screen, if it is not visible, I change the style and make that box fixed. Following code should give the idea what I am doing:
methods: {
onScroll () {
if ($('#divId').visible(false, false, 'vertical')) { // This is div from the compA, so I want to make sure it is rendered first and it is visible
this.isFixed = false
} else {
this.isFixed = true
}
}
},
mounted () {
window.addEventListener('scroll', this.onScroll() }
},
destroyed () {
window.removeEventListener('scroll', this.onScroll)
}
I dont want to make those in same component as one reason is it dont make sense as the nature of these components, and other I use compA at many places, while compB is specific to only one page. Also layout of these does not allow me to make compB child of compA as suggested in comments.
Any suggestions are welcome.

An option with events:
<!-- Parent -->
<div>
<comp-a #rendered="rendered = true"></comp-a>
<component :is="compB"></component>
</div>
<script>
// import ...
export default {
components: { CompA, CompB },
watch: {
rendered: function (val) {
if (val) this.compB = 'comp-b';
}
},
data() {
return {
rendered: false,
compB: null
}
}
}
</script>
<!-- Component B -->
<script>
export default {
mounted() {
this.$emit('rendered');
}
}
</script>

After going through the edit I realised that the dependency is not data driven but event driven (onscroll). I have tried something and looks like it works (the setTimeout in the code is for demonstration).
My implementation is slightly different from that of Jonatas.
<div id="app">
RenderSwitch: {{ renderSwitch }} // for demonstration
<template v-if='renderSwitch'>
<comp-a></comp-a>
</template>
<comp-b #rendered='renderSwitchSet'></comp-b>
</div>
When the component-B is rendered it emits an event, which just sets a data property in the parent of both component-A and component-B.
The surrounding <template> tags are there to reduce additional markup for a v-if.
The moment renderSwitch is set to true. component-a gets created.

Getting the event source from custom events in Vue?

I'm building a Vue component that consists of an unspecified number of child components. Only one child component is visible at all times, and the user can only switch between child components when the one currently visible has emitted an is-valid event.
I want to keep this decoupled, such that children do not know about their parent and only communicate by emitting events. This also means that the children do not know their position within the parent component.
So, the parent component somehow has to keep track of which child the event came from. If the event came from the right child (the one currently visible) then some buttons are activated that allows the user to go to the next or previous child.
Here's my code so far:
HTML
<div id="app">
<template id="m-child">
<div>
<button v-on:click="setstate(true)">Valid</button>
<button v-on:click="setstate(false)">Invalid</button>
</div>
</template>
<template id="m-parent">
<div>
<m-child v-on:newstate="newchildstate"></m-child>
<m-child v-on:newstate="newchildstate"></m-child>
<m-child v-on:newstate="newchildstate"></m-child>
</div>
</template>
<m-parent></m-parent>
</div>
JS
Vue.component('m-child', {
template: '#m-child',
data: function() {
return {};
},
methods: {
setstate: function (valid) {
this.$emit('newstate', valid);
}
}
});
Vue.component('m-parent', {
template: '#m-parent',
methods: {
newchildstate: function (valid) {
console.log('valid:' + valid + ', but where from?');
}
}
});
new Vue({
el: '#app'
});
Of course I could hardcode an index on the child event binding:
<m-child v-on:newstate="newchildstate(0, $event)"></m-child>
<m-child v-on:newstate="newchildstate(1, $event)"></m-child>
<m-child v-on:newstate="newchildstate(2, $event)"></m-child>
But that would make the whole setup a lot less modular, I just want to be able to plug in a number of children in the DOM and make it work right away.
I've looked at the API for Vue events and there doesn't seem to be a way to get the source from the event object.

This depends on what you want to receive back, my personal preference is to pass in a prop to set a unique id and pass it back in the $emit:
<m-child v-on:newstate="newchildstate" :id="1"></m-child>
<m-child v-on:newstate="newchildstate" :id="2"></m-child>
<m-child v-on:newstate="newchildstate" :id="3"></m-child>
Then in your child component you can emit an object with the state and id the id:
Child:
this.$emit('newstate', {id: this.id, state: valid});
Parent:
newchildstate: function (valid) {
console.log('valid:' + valid.state + ', from' + valid.id);
}
I realise that this doesn't look hugely different from your hard coded example, but at some point your parent is going to want to deal with the event, so you could set up an array in data with the initial states and then use a v-for:
data: {
children: [true, false, false] // setup states
}
You would then do:
<div v-for="(state, index) in states">
<m-child v-on:newstate="newchildstate" :id="index"></m-child>
</div>
And in your view model:
methods: {
newchildstate: function(valid) {
this.$set(this.states, valid.id, valid.state);
}
}
Here's a JSFiddle that initiates the array dynamically via a prop and sets up the child components: https://jsfiddle.net/2y9727e2/

Detect component content change in Ractive.js

Is there any way of detecting when the content of a component changes?
For example:
HTML:
<component>
<div>{{name}}</div>
</component>
JS:
component = Ractive.extend({
on...: function () {
// invoked when the inner HTML changes
}
});
I use {{yield}} so the content is rendered in the context of the parent.
For now I'll have to pass name to the component just for the purpose of observing changes (even though I don't need the value in the context of the component). (Or I'll add a function that I can call).
<component changes="{{name}}">
<div>{{name}}</div>
</component>
Any ideas?

It's possible, but a bit hacky.
http://plnkr.co/edit/YoTZpyTTyCyXijEteGkg?p=preview
<comp>
{{name}} hi {{thing}}
</comp>
comp = Ractive.extend({
template: '<div>{{yield}}</div>',
oncomplete: function() {
var self = this;
self.partials.content.forEach(function(partial) {
if (partial.r) {
self.parent.observe(partial.r, function(newValue) {
console.log(partial.r + ' changed to ', newValue)
}, {init: false});
}
});
}
})
Yield/Content are really just special partials, so this will loop through the items in that partial and set up an observer for each keypath.
This demo only works with simple expressions like {{foo}}. If you have more complicated things inside the partial you'll have to inspect the rendered partial to figure out what keypath you want to observe the parent on.