Why sometimes 'this' works and sometimes doesn't in Vue template? - vue.js

Have a situation in which there are two different components, that have templates in which there are 'this' used. Removing all 'this' from templates right now, but saw this situation and got curios why it is happening like this.
In this case it throws error:
<a :href="`${this.$locale() ? "Yes" : "No}`">
In this case it works:
<title :lang="this.$locale()">
These are just examples, but is there a reason that one works and other throws error? Couldn't find any information on this in Vue documentation. Could this be because of ternary operation?

First of all, to be clear for the people reading this, you shouldn't use this inside Vue SFC templates.
To anwser, that's because of how Vue compiles your template and its properties. I'm not an expert on Vue internal mecanics so please take what I say with caution.
:lang="this.$locale() Here, it could be that Vue removes the this reference at build time.
:href="`${this.$locale() ? "Yes" : "No}`" Here you're using a string interpolation, which is evaluated at runtime. Vue has no way to remove the this safely, because it could be refering to something else than the component instance. So this just stays as is in the final bundle and breaks at runtime.
This is just my guess from my understanding of Vue. I think only a Vue maintainer / contributor could anwser this properly.

Related

VueJS 3 $delete component

How can I make a component delete itself in Vue 3?
In Vue 2 you could say this.$destroy(); But apparently that got removed and there is no replacement for it: "vm.$delete removed (no longer needed)" (from https://v3-migration.vuejs.org/breaking-changes/migration-build.html#fully-compatible )
Not sure why it's no longer needed since they don't explain why or give an alternative and I can definitely still see the need for something like this.
For now I just use a <div v-if="show"> but it seems a bit of a hack.
From Vue 3 docs you can find it here: https://v3-migration.vuejs.org/breaking-changes/introduction.html#removed-apis that you don't need to manually manage the component lifecycle anymore. So I guess you can deprecate the piece of code executing ".$destroy()".

How to get rid of Mismatching childNodes vs. VNodes in NuxtJs [duplicate]

I am using Nuxt.js / Vuejs for my app, and I keep facing this error in different places:
The client-side rendered virtual DOM tree is not matching server-rendered content.
This is likely caused by incorrect HTML markup, for example nesting block-level elements inside <p>, or missing <tbody>.
Bailing hydration and performing full client-side render.
I would like to understand what is the best way to debug this error? Is their a way I can record/get the virtual DOM tree for client and server so I could compare and find where the error lies?
Mine is a large application and manually verifying is difficult.
Partial answer: with Chrome DevTools, you can localize the issue and see exactly what element caused the issue. Do the following (I did that with Nuxt 5.6.0 and Chrome 64.0.3282.186)
Show DevTools in Chrome (F12)
Load the page that causes "the client-side rendered virtual DOM tree..." warning.
Scroll to the warning in DevTools console.
Click at the source location hyperlink of the warning (in my case it was vue.runtime.esm.js:574).
Set a breakpoint there (left-clicking at line number in the source code browser).
Make the same warning to appear again. I'm not saying it is always possible, but in my case I simply reloaded the page. If there are many warnings, you can check the message by moving a mouse over msg variable.
When you found your message and stopped on a breakpoint, look at the call stack. Click one frame down to call to "patch" to open its source. Hover mouse over hydrate function call 4 lines above the execution line in patch. Hyperlink to the source of hydrate would open.
In the hydrate function, move about 15 lines from the start and set a breakpoint where false is returned after assertNodeMatch returned false. Set the breakpoint there and remove all other breakpoints.
Make the same warning to happen again. Now, when breakpoint is hit, execution should stop in the hydrate function. Switch to DevTools console and evaluate elm and then vnode. Here elm seem to be a server-rendered DOM element while vnode is a virtual DOM node. Elm is printed as HTML so you can figure out where the error happened.
For me this error happened cuz get Array list in AsyncData and rendered <tr> tags by v-for, i put v-for codes in <client-only> blocks and problem solved
This error can be really painfull to debug. In order to quickly get the element causing an issue edit node_modules/vue/dist/vue.esm.js and add the following lines :
// Search for this line:
function hydrate (elm, vnode, insertedVnodeQueue, inVPre) {
var i;
var tag = vnode.tag;
var data = vnode.data;
var children = vnode.children;
inVPre = inVPre || (data && data.pre);
vnode.elm = elm;
// Add the following lines:
console.log('elm', elm)
console.log('vnode', vnode)
console.log('inVpre', inVPre)
// ...
You will get in the console the failing node.
There are a lot of ways of fixing this issue, but most of them are not actual fixes, just hacky band-aids. To note a few:
wrap it into <client-only> tags, beware of some important details tho
using a v-show instead of a v-if
trying to hack some lifecycles
etc...
I highly recommend reading this gorgeous article written by Alexander Lichter
https://blog.lichter.io/posts/vue-hydration-error/
He'll explain you that you should diagnose why this happens and fix the actual issue.
Basically each time something is different from what was generated on the server and what is available when done hydrating on the client will cause this error.
Some of which are:
invalid HTML (having a block element inside of a <p>, same goes for an a tag nested into another, etc...)
3rd party scripts messing around with your components
different state on server vs client
any random is risky (new Date() for example)
any page related to authentication
I highly recommend reading the article to understand in Alexandre's own words how to handle this kind of issue. If you're in a hurry you could always use one band-aid fix but try to actually fix the issue for the best performance and to keep the code clean.
I had the same issue as of nuxt version 2.14.0 while implementing vue-particles package. The fix was to surround the tags with no-ssr and it fixed the issue.
EDIT:
Updated variant of the solution (if Nuxt version is above 2.9.0)
<client-only>
<vue-particles>
</vue-particles>
</client-only>
Old solution:
<no-ssr>
<vue-particles>
</vue-particles>
</no-ssr>
Thanks to budden73's answer, I did a little improvement on the debug process.
Open dev tool
click on the warn message, and click on the first line of the warn message, you will be directed to the Sources panel, with a file name vue.runtime.esm.js?xxxx
ctrl+f to search the above file for assertNodeMatch, not the function, but like:
if (process.env.NODE_ENV !== 'production') {
if (!assertNodeMatch(elm, vnode, inVPre)) {
return false
}
}
Add a break point at the line return false
Refresh the page, and the breakpoint will be triggered.
At the right side of the Sources panel, Under Scope->Local, click on the elm element, you will be directed back to the Elements panel.
The above element is the client side rendered element, compare with your code to see the difference.
If you can't find the source of the bug, the brutal way to fix it is using nuxt's <client-only> tag.
Another likely brutal way is described here. Add an isHydrate variable which default is false, set to true in mounted hook, and render the element after the variable set to true.
For Nuxt version above 2.10 it doesn't need to install nothing, just use the default component <client-only> as mentioned https://nuxtjs.org/api/components-client-only/.
Check the previous warning:
In "nuxt": "^2.12.2", You can spot the cause easily from the previous warning.
In my case:
Incorrect
<nuxt-link to="/game42day">
<a>Game For Today</a>
</nuxt-link>
Correct:
<nuxt-link to="/game42day">
Game For Today
</nuxt-link>
If you're rendering a component conditionally with v-if, then you have two options to solve the problem:
The first one is wrapping the element in <no-ssr></no-ssr> tag.
The second approach is replacing v-if with v-show, here is the link to Vue docs.
Turns out, in my case, I had HTML comment tags , which was causing this stupid, annoying error. Took me too long to figure it out but in case it helps someone.
In my case I had to change this:
<v-expansion-panel-header v-text="name" />
to this:
<v-expansion-panel-header>{{ name }}</v-expansion-panel-header>
I also get many errors due to this problem. I list two cases I often encounter, hope can help you.
With vuetify button, when you create a common component, you should use: <v-btn>{{text}}</v-btn>. Example:
<template>
<v-btn
:width="width"
:color="color"
:class="[rounded ? 'rounded-pill' : 'rounded-lg',textColor]"
v-on:click="onClick"
elevation="0"
:outlined="outlined"
:type="type"
:name="name"
:form="form"
:disabled="disabled"
v-bind="$attrs"
>{{ text }}</v-btn>
</template>
Don't use v-html with <p> tag.
Not use: <p v-html='html'></p>.
Use: <div v-html='html'></div>.
Besides, if you use <client-only></client-only>, this problem is definitely solved, but if you need to SEO page or show google ads, it is not good solution.
Ok this is going to sound silly. I tried a bunch of different solutions for about 15 mins such as restarting the server and deleting the .nuxt directory but I was too lazy to use #budden73's big brain solution. What ended up working for me was simply restarting my computer, give it a shot.
What I have found so far from observation is that when you are using third party packages like jQuery (specially), they sometimes inject html tags into the dom. So Vue/Nuxt looses track of the dom tree and starts complaining.
I was having the same problem and after a while I removed all jQuery and replaced jQuery functionality with Vuejs and those error were all gone.
See here for an example of how to deal with integrations (e.g. Google Analytics or FB Pixel) that modify the DOM. Basically create a plugin and exclude from SSR.
https://nuxtjs.org/faq/ga
What about:
extend (config, ctx) {
config.resolve.symlinks = false
}
See this [Vue warn]: The client-side rendered virtual DOM tree is not matching server-rendered content ( Nuxt / Vue / lerna monorepo )
Now that you found the code causing the problem, the first thing you should do is to verify that your markup (possibly coming from an API) is valid. Code like <p><p>Text</p></p> is not valid because a p element doesn’t allow other block elements (like a paragraph tag) inside.
Be aware, that tags are not allowed to have block level elements like <div> or <p> as children. These <span> tags are used default tag for Vue’s transitions though. You can change that though via <Transition tag="div">.
Check if have used any block-level element inside the inline element.
for example: inside , inside
If you have used an HTML table make sure you have used the tag
In my case, I changed my codes from
<p v-html="$md.render(post.content)"></p>
to
<p>{{ $md.render(post.content) }}</p>
In my case this problem was caused by markdownit module, I solved it by changing the html markup used with v-html. I was with <p> at the beginning and I ended with <div>.
I have some <p> in my v-html render (with $md.render()) so take care if you have same problems with different markups.

VueJS with HAML/Jade/Pug-like templating

I'm using both Vue.js and HAML in my current project. The templates are parsed by HAML, converted into HTML, then parsed by Vue. For instance:
#pagecontent.nonscrolling
%h2 Demand forecasts
%label{ for:"location-type" } Select location type
%select.form-control#location-type{ v-model:"locationType" }
%option{ v-bind:value:"'foo'" } Foo
It works ok, but it's a bit disconcerting worrying whether all the Vue syntax will make it unscathed through the HAML parser.
But I really like this type of succinct, angle-bracket-less template.
Is there is a cleaner way to achieve this? Some add-on to Vue that supports something similar?
Don't worry to much. There is nothing wrong about using preprocessors. I mean vue depends on wepback where everything is being preprocessed in one way or an other. Out of the box you can use pug with vue so I put more trust in it. It works fine for me without any unexpected problems. Both have the nesting through indentation in common and this is something that starts to be confusing with longer source codes. So I use pug mainly in short components and nest them using named slots into bigger ones.
Your code - pug version (as far I can guess what this HAML code should do)
<template lang="pug">
#pagecontent.nonscrolling
h2 Demand forecasts
label(for="location-type") Select location type
select.form-control#location-type(v-model="locationType")
option(v-bind:value="foo") Foo
</template>
The whole Vuetifyjs website is made with pug:
Vuetifyjs.com Source Code

Vue JSX bind to class name

I'm building a simple TodoMVC app using Vue + JSX, but the documentation seems to be seriously lacking. Thus, I'm writing down the points I need to address as part of a CR to the appropriate projects. The only document I've read as of yet is the guide, which doesn't cover much JSX at all. I don't know much about how the framework works yet, but I sure prefer using the render method over the string templates for performance/network reasons.
question
What's the proper way to create a class name binding in Vue + JSX? In my TodoItem component, creating either a class or className attribute makes Babel throw a compile error complaining the API is deprecated (and suggesting I add several seemingly unrelated dependencies to the mix). Plus, including the class property in the data object seems to change nothing.
secondary question
The lack of documentation, plus the wording on the guide gives the impression JSX is not the "proper" way to write Vue components. Is that so? What's the idiomatic way to do it, given I don't want to ship the compiler along with my app?
links
code on codepan
I sure prefer using the render method over the string templates for performance/network reasons.
If you're writing *.vue files and bundling them with vue-loader (Webpack), the HTML template gets compiled into a JavaScript render function anyway, so there isn't really any kind of performance issues in that sense.
On the other hand, if you're writing your Vue components with string templates like this:
new Vue({
template: '<div>Hello</div>'
})
then you'll need the Vue template compiler at runtime to convert the string into a render function.
Typically people would opt for writing render functions manually if they need to do something specific that would be difficult/impossible to do with the HTML template alone.
You've probably already read the docs, but just in case, the relevant sections are:
Render Functions & JSX
The Data Object In-Depth
babel-plugin-transform-vue-jsx Usage
What's the proper way to create a class name binding in Vue + JSX?
You would just bind to the class attribute like you would any other attribute:
<div class={this.klass}>
data() {
return {
klass: 'foo'
}
}
The lack of documentation, plus the wording on the guide gives the impression JSX is not the "proper" way to write Vue components. Is that so? What's the idiomatic way to do it, given I don't want to ship the compiler along with my app?
JSX is definitely supported, but it is not the recommended approach. The recommended approach is to write *.vue files and load them with vue-loader (if using Webpack).
Vue comes in two versions, one with and one without the template compiler. The one with the compiler included is only for development and should not be used for production builds (unless you require string template to render function compilation at runtime, which is unlikely). See Explanation of Build Files for more info.
Typically you write HTML string templates, and they get compiled to render functions (by vue-loader) at build time.

Vue.JS check if vue-i18n is installed

i got a little Problem, i'm creating a vuejs package in which i use vue-i18n to translate things.
The Problem is, if the user haven't got vue-i18n installed it breaks the package (obviously since i use it).
Do you know a way to prevent this?
My first approach was to just v-if the translations in the template to check if i18n is registered within window, but that obviously won't work if a user names the object differently.
you can check if this.$i18n exists