In vue 2 v-html require to render an extra wrapping tag. But I'm trying something like following.
<select v-model="coutnry">
// here the options to be rendered.
</select>
<script>
...
data()}{
return{
countryTags:`<option value="BD">Bangladesh</option>`
}
}
</script>
Since, here I can't render any extra html tag, I tired <template v-html="countryTags"> and that didn't worked. The other solution around stackoverlflow seems little confusing. what's the proper solution ?
Unfortunately, Vue does not provide an easy way to accomplish this (More details about the reasons can be found here: https://github.com/vuejs/vue/issues/7431)
As explained there you can create a functional component to just render the HTML without a wrapper element:
Vue.component('html-fragment', {
functional: true,
props: ['html'],
render(h, ctx) {
const nodes = new Vue({
beforeCreate() { this.$createElement = h }, // not necessary, but cleaner imho
template: `<div>${ctx.props.html}</div>`
}).$mount()._vnode.children
return nodes
}
})
This component is created by a Vue core member (LinusBorg): https://jsfiddle.net/Linusborg/mfqjk5hm/
Related
I am curious if it is better to include methods within loops instead of using v-if. Assume the following codes work (they are incomplete and do not)
EX: Method
<template >
<div>
<div v-for="(d, i) in data" v-bind:key="i">
<span v-on:click="insertPrompt($event)">
{{ d }}
</span>
</div>
</div>
</template>
<script>
export default {
data() {
data:[
.....
]
},
methods:{
insertPrompt(e){
body.insertBefore(PROMPT)
}
}
}
</script>
The DOM would be updated via the insertPrompt() function which is just for display
EX: V-IF
//Parent
<template >
<div>
<div v-for="(d, i) in data" v-bind:key="i">
<child v-bind:data="d"/>
</div>
</div>
</template>
<script>
import child from './child'
export default {
components:{
child
},
data() {
data:[
.....
]
},
}
</script>
//Child
<template>
<div>
<span v-on:click="display != display">
{{ d }}
</span>
<PROMPT v-if="display"/>
</div>
</template>
<script>
import child from './child'
export default {
components:{
child
},
data(){
return {
display:false
}
},
props: {
data:{
.....
}
},
}
</script>
The PROMPT is a basic template that is rendered with the data from the loop data click.
Both methods can accomplish the same end result. My initial thought is having additional conditions within a loop would negatively impact performance?!?!
Any guidance is greatly appreciated
Unless you are rendering really huge amounts of items in your loops (and most of the times you don't), you don't need to worry about performance at all. Any differences will be so small nobody will ever notice / benefit from having it a tiny touch faster.
The second point I want to make is that doing your own DOM manipulations is often not the best idea: Why do modern JavaScript Frameworks discourage direct interaction with the DOM
So I would in any case stick with the v-if for conditionally rendering things. If you want to care about performance / speed here, you might consider what exactly is the way your app will be used and decide between v-if and v-show. Citing the official documentation:
v-if is “real” conditional rendering because it ensures that event
listeners and child components inside the conditional block are
properly destroyed and re-created during toggles.
v-if is also lazy: if the condition is false on initial render, it
will not do anything - the conditional block won’t be rendered until
the condition becomes true for the first time.
In comparison, v-show is much simpler - the element is always rendered
regardless of initial condition, with CSS-based toggling.
Generally speaking, v-if has higher toggle costs while v-show has
higher initial render costs. So prefer v-show if you need to toggle
something very often, and prefer v-if if the condition is unlikely to
change at runtime.
https://v2.vuejs.org/v2/guide/conditional.html#v-if-vs-v-show
There are numerous solutions to solving this issue, but let's stick to 3. Options 2 and 3 are better practices, but option 1 works and Vue was designed for this approach even if hardcore developers might frown, but stick yoru comfort level.
Option 1: DOM Manipulation
Your data from a click, async, prop sets a condition for v-if or v-show and your component is shown. Note v-if removes the DOM element where v-show hides the visibility but the element is still in the flow. If you remove the element and add its a complete new init, which sometimes works in your favor when it come to reactivity, but in practice try not to manipulate the DOM as that will always be more expensive then loops, filters, maps, etc.
<template >
<div>
<div v-for="(d, i) in getData"
:key="i">
<div v-if="d.active">
<child-one></child-one>
</div>
<div v-else-if="d.active">
<child-two></child-two>
</div>
</div>
</div>
</template>
<script>
import ChildOne from "./ChildOne";
import ChildTwo from "./ChildTwo";
export default {
components: {
ChildOne,
ChildTwo
},
data() {
return {
data: [],
}
},
computed: {
getData() {
return this.data;
},
},
mounted() {
// assume thsi woudl come from async but for now ..
this.data = [
{
id: 1,
comp: 'ChildOne',
active: false
},
{
id: 2,
comp: 'ChildTwo',
active: true
},
];
}
}
</script>
Option 2: Vue's <component> component
Always best to use Vue built in component Vue’s element with the is special attribute: <component v-bind:is="currentTabComponent"></component>
In this example we pass a slug or some data attribute to activate the component. Note we have to load the components ahead of time with the components: {}, property for this to work i.e. it has to be ChildOne or ChildTwo as slug string. This is often used with tabs and views to manage and maintain states.
The advantage of this approach is if you have 3 form tabs and you enter data on one and jump to the next and then back the state / data is maintained, unlike v-if where everything will be rerendered / lost.
Vue
<template >
<div>
<component :is="comp"/>
</div>
</template>
<script>
import ChildOne from "./ChildOne";
import ChildTwo from "./ChildTwo";
export default {
components: {
ChildOne,
ChildTwo
},
props: ['slug'],
data() {
return {
comp: 'ChildOne',
}
},
methods: {
setComponent () {
// assume prop slug passed from component or router is one of the components e.g. 'ChildOne'
this.comp = this.slug;
}
},
mounted() {
this.nextTick(this.setModule())
}
}
</script>
Option 3: Vue & Webpack Async and Dynamic components.
When it comes to larger applications or if you use Vuex and Vue Route where you have dynamic and large number of components then there are a number of approaches, but I'll stick to one. Similar to option 2, we are using the component element, but we are using WebPack to find all Vue files recursively with the keyword 'module'. We then load these dynamically / asynchronous --- meaning they will only be loaded when needed and you can see this in action in network console of browser. This means I can build components dynamically (factory pattern) and render them as needed. Example, of this might be if a user adds projects and you have to build and config views dynamically for projects created e.g. using vue router you passed it a ID for a new project, then you would need to dynamically load an existing component or build and load a factory built one.
Note: I'll use v-if on a component element if I have many components and I'm unsure the user will need them. I don't want to maintain state on large collections of components because I will end up memory and with loads of observers / watches / animations will most likely end up with CPU issues
<template >
<div>
<component :is="module" v-if="module"/>
</div>
</template>
<script>
const requireContext = require.context('./', true, /\.module\.vue$/);
const modules = requireContext.keys()
.map(file =>
[file.replace(/(.*\/(.+?)\/)|(\.module.vue$)/g, ''), requireContext(file)]
)
.reduce((components, [name, component]) => {
// console.error("components", components)
components[name] = component.default || component
return components
}, {});
export default {
data() {
return {
module: [],
}
},
props: {
slug: {
type: String,
required: true
}
},
computed: {
getData() {
return this.data;
},
},
methods: {
setModule () {
let module = this.slug;
if (!module || !modules[module]) {
module = this.defaultLayout
}
this.module = modules[module]
}
},
mounted() {
this.nextTick(this.setModule())
}
}
</script>
My initial thought is having additional conditions within a loop would negatively impact performance?
I think you might be confused by this rule in the style guide that says:
Never use v-if on the same element as v-for.
It's only a style issue if you use v-if and v-for on the same element. For example:
<div v-for="user in users" v-if="user.isActive">
But it's not a problem if you use v-if in a "child" element of a v-for. For example:
<div v-for="user in users">
<div v-if="user.isActive">
Using v-if wouldn't have a more negative performance impact than a method. And I'm assuming you would have to do some conditional checks inside your method as well. Remember that even calling a method has some (very small) performance impact.
Once you use Vue, I think it's a good idea not to mix it up with JavaScript DOM methods (like insertBefore). Vue maintains a virtual DOM which helps it to figure out how best to update the DOM when your component data changes. By using JavaScript DOM methods, you won't be taking advantage of Vue's virtual DOM anymore.
By sticking to Vue syntax you also make your code more understandable and probably more maintainable other developers who might read or contribute to your code later on.
I wrote a wrapper directive that utilizes vue's Render function.
Inside the render function all it does is:
render: function(createElement) {
const compiled = Vue.compile(this.$props.template);
return compiled.render.call(this, createElement);
}
I'm using like:
<Render v-for="item in itemsToRender" :key="item.id" />
This works for native html elements:
const itemsToRender = ['<p>test</p>', '<h1>HELLO</h1>'];
However if I pass in my own custom directive like
<my-directive></my-directive>
Then vue will complain about unknown components. This is probably because I don't have the custom directive imported/required in the render directive's context. Is there a work around for this? The reason I need to have this wrapper directive do the compile is because libraries like vue.Draggable, rely on 'v-for' to reorder the list elements. However, I want to be able to have different components be draggable, which is why i'm passing just templates to compile into the v-for.
You can use the component tag. Check out: https://v2.vuejs.org/v2/guide/components.html#Dynamic-Components
I have made an example here: https://codepen.io/bergur/pen/jjwzEq
The flow is roughly this:
I register the components within my app
List them up in the listItemsToRender data property
Use the <component> tag to render them
Here is the code
new Vue({
name: 'main',
el: '#main',
components: {
CompA,
CompB
},
data() {
return {
header: 'Multiple components',
itemsToRender: [CompA, CompB]
}
},
template: `
<div>
{{ header }}
<component v-for="item in itemsToRender" :is="item" />
</div>`
})
I'm trying to solve this for Nuxt
Codesandbox of a WIP not working: https://codesandbox.io/s/zw26v3940m
OK, so I have WordPress as a CMS, and it's outputting a bunch of HTML. A sample of the HTML looks like this:
'<h2>A heading tag</h2>
<site-banner image="{}" id="123">Slot text here</site-banner>
<p>some text</p>'
Notice that it contains a Vue component <site-banner> that has some props on it (the image prop is a JSON object I left out for brevity). That component is registered globally.
I have a component that we wrote, called <wp-content> that works great in Vue, but doesn't work in Nuxt. Note the two render functions, one is for Vue the other is for Nuxt (obviously this is for examples sake, I wouldn't use both).
export default {
props: {
html: {
type: String,
default: ""
}
},
render(h, context) {
// Worked great in Vue
return h({ template: this.html })
}
render(createElement, context) {
// Kind of works in Nuxt, but doesn't render Vue components at all
return createElement("div", { domProps: { innerHTML: this.html } })
}
}
So the last render function works in Nuxt except it won't actually render the Vue components in this.html, it just puts them on the page as HTML.
So how do I do this in Nuxt? I want to take a string of HTML from the server, and render it on the page, and turn any registered Vue components into proper full-blown Vue components. Basically a little "VueifyThis(html)" factory.
This was what worked and was the cleanest, thanks to Jonas Galvez from the Nuxt team via oTechie.
export default {
props: {
html: {
type: String,
default: ""
}
},
render(h) {
return h({
template: `<div>${this.html}</div>`
});
}
};
Then in your nuxt.config.js file:
build: {
extend(config, ctx) {
// Include the compiler version of Vue so that <component-name> works
config.resolve.alias["vue$"] = "vue/dist/vue.esm.js"
}
}
And if you use the v-html directive to render the html?
like:
<div v-html="html"></div>
I think it will do the job.
Here's a solution on codesandbox: https://codesandbox.io/s/wpcontent-j43sp
The main point is to wrap the dynamic component in a <div> (so an HTML tag) in the dynamicComponent() template, as it can only have one root element, and as it comes from Wordpress the source string itself can have any number of top level elements.
And the WpContent component had to be imported.
This is how I did it with Nuxt 3 :
<script setup lang="ts">
import { h } from 'vue';
const props = defineProps<{
class: string;
HTML: string
}>();
const VNode = () => h('div', { class: props.class, innerHTML: props.HTML })
</script>
<template>
<VNode />
</template>
There was not need to update nuxt.config.ts.
Hopefully it will help some of you.
I made some changes to your codesandbox. seems work now https://codesandbox.io/s/q9wl8ry6q9
Things I changed that didn't work:
template can only has one single root element in current version of Vue
v-bind only accept variables but you pass in a string.
I'm new to Vue.js
I want to render a script tag inside a variable (data string).
I tried to us a v-html directive to do so, but it doesn't work Nothing is rendered
Any way I can achieve this?
I'd place a v-if directive on the script tag and put the content of it in a variable.
<script v-if="script">
{{script}}
</scrip>
If I understand you correctly, my answer is:
<template>
<div>
{{ strWithScriptTag }}
</div>
</template>
<script>
export default {
name: 'Example',
methods: {
htmlDecode(input) {
const e = document.createElement('div')
e.innerHTML = input
return e.childNodes[0].nodeValue
},
},
computed: {
strWithScriptTag() {
const scriptStr = '<script>https://some.domain.namet</script>'
return this.htmlDecode(scriptStr)
}
},
}
</script>
I think that by safety vue is escaping your <script> automatically and there is no way to avoid this.
Anyway, one thing you can do is eval(this.property) on created() lifecycle hook.
data: {
script: 'alert("this alert will be shown when the component is created")'
},
created() {
eval(this.script)
}
Use it with caution, as stated in vue js docs, this may open XSS attacks in your app
I wrote a simple template-substitution component in VueJS as a single-file component. It doesn't have many features: just one prop, and I also made a computed property to encapsulate some tricky transformations that are done to that prop before it can be used in the template. It looks something like the following:
<template>
...some-html-here...
<a :href="myHref">...</a>
...
</template>
<script>
export default {
name: 'MyComponent',
props: {
href: { type: String, required: true },
},
computed: {
myHref() {
let result = this.href;
// several lines of complicated logic making substitutions and stuff
// ...
return result;
}
}
};
</script>
Now I think this should really be a functional component, as it has no state, no data, no reactivity, and so lunking around a whole instance is wasteful.
I can make this functional just by adding the 'functional' attribute to my <template>. In a functional component, of course, there are no such things as computed properties or methods or whatever. So my question is: where can I put my several lines of complicated logic? I don't want to have to embed this directly into my template, especially as it is used in multiple places. So where can I put code to transform my input props and make them ready to use in my template?
Great question.I was trying to find the same answer and i ended up with the following which i don't know if it is a good way to do though.
The "html" part:
<template functional>
<div>
<button #click="props.methods.firstMethod">Console Something</button>
<button #click="props.methods.secondMethod">Alert Something</button>
</div>
</template>
The "js" part:
<script>
export default {
props: {
methods: {
type: Object,
default() {
return {
firstMethod() {
console.log('You clicked me')
},
secondMethod() {
alert('You clicked me')
}
}
}
}
}
}
</script>
See it in action here
Make sure to read about functional components at docs
NOTE: Be aware using this approach since functional components are stateless (no reactive data) and instanceless (no this context).