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.
Example of the HTML of a dropdown element:
<div aria-owns="ember-basic-dropdown-content-ember1234" tabindex="0" data-ebd-id="ember1234-trigger" role="button" id="ember1235" class="ember-power-select-trigger ember-basic-dropdown-trigger ember-view"> <!---->
<span class="ember-power-select-status-icon"></span>
</div>
The xpath and CSS selector also contain the same ember id.
xpath : //*[#id="ember1235"]
css selector : #ember1235
The ember id would change from id="ember1235" to say, id="ember1265" when there is a change in the UI.
I am using id to locate the element. But every time it changes I need to modify the code. Is there any other attribute I could use for Ember JS UI elements?
There is quite a lot to discuss in your question but hopefully we will have a good answer for you #PriyaK
The first thing to mention is that Ember IDs may not be the best method to select an element in the DOM. As you have already mentioned, they can change from time to time and also it doesn't really give you a great semantic thing to select in your selenium test so it might seem a bit out of context when looking back.
One thing that you could try is to either pass a class to the ember-power-select component (the one that provides the HTML that you used in your example) and use that to select the element, something like:
<PowerSelect
#class="my-fancy-class"
as |name|
>
{{name}}
</PowerSelect>
Then you should be able to select the selected value by using the CSS selector .my-fancy-class span (because the component outputs the selected value in a span)
We just tried this in an example app but it didn't actually work 🤔 Never fear, you can also do something like this and it should work with the same selector as before:
<div class="my-fancy-class">
<PowerSelect as |name|>
{{name}}
</PowerSelect>
</div>
This is fine, but there are also a few issues using classes for selectors in tests. One example of a problem that might crop up is that your tests might all suddenly stop working if you did a style refactor and changed or removed some of the classes on your elements. One technique that has become popular in the Ember community is to use data-test- attributes on your DOM nodes like this:
<div data-test-my-fancy-select>
<PowerSelect
#class="my-fancy-class"
as |name|
>
{{name}}
</PowerSelect>
</div>
which can then be accessed by the following selector: [data-test-my-fancy-select] span. This is great for a few reasons! Firstly it separates the implementation of your application and tests from your styling and avoids the issue I described above. The second benefit of this method is that using what #Gokul suggested in the comments, the ember-test-selectors package, you can make use of these data-test- selectors in your development and test environments but they will be automatically removed from your production build. This is great to keep your DOM clean in production but also, depending on the size of your application, could save you a reasonable amount of size in your templates on aggregate.
I know you say that you are using selenium for your testing but it's also worth mentioning that if you're using the built-in Ember testing system you will be able to make use of some testing helpers that addons may provide you. ember-power-select is one of those addons that provides specific testing helpers and you can read more about it in their documentation: https://ember-power-select.com/docs/test-helpers
I hope this answers any questions you had!
This question was answered as part of "May I Ask a Question" Season 3 Episode 1. If you would like to see us discuss this answer in full you can check out the video here: https://www.youtube.com/watch?v=1DAJXUucnQU
I'm making a one-page website for a friend of mine. She's a fashion designer, and she would love to have a one-page website based on the "Stylish Portfolio" Bootstrap template --> http://startbootstrap.com/stylish-portfolio
However, I want to put in a lightbox gallery in the section below where it says "Some of our work".
I was thinking of getting the BlueImp Lightbox gallery or the Bootstrap Lightbox: http://www.jasonbutz.info/bootstrap-lightbox/#usage
Both match what I was looking for.
However, I have tried to insert it into the HTML-code, but without any luck!
Does anybody have any experience in inserting/adding lightbox galleries to a Bootstrap template? And if so, how should I approach this task?
Like the comments from your question, they wanted to see your code so they know where and how they can help you. It would also let us know how much code we would need to supply without actually spoon-feeding you the answers so that you can get your answers as well as still learn :)
With that, I'm gonna assume that you're a beginner and thus supply most of the codes that you need as well as explanations on what I'm doing. I'm gonna take bootstrap-lightbox as an example.
First off, you need to download the files from the site. After downloading the files, you would be able to see that this contains 4 files, namely bootstrap-lightbox.css, bootstrap-lightbox.js and their min files. (min files are just compressed versions of the files in order to lessen its size)
Now, it's basically just needing to plug-in those files into your project.
Assuming that you put the files into their respective js and css folders in your project, this is how they would look like:
<link href="css/bootstrap-lightbox.css" rel="stylesheet"> //plug this inside your <head> tags
<script src="js/bootstrap-lightbox.js"></script>
After plugging those in your files, then its a matter of just using the html code that you found in the site :)
<div id="demoLightbox" class="lightbox hide fade" tabindex="-1" role="dialog" aria-hidden="true">
<div class='lightbox-content'>
<img src="image.png">
<div class="lightbox-caption"><p>Your caption here</p></div>
</div>
</div>
Solved.
I used BlueImp instead to insert a lightbox gallery :-)
I am wondering if it is possible (but I have a hunch it's not..) to retrieve the absolute URL of an image that is loaded by a specific CSS class.
For example:
<div class="rabbit">
rabbit in css has a background image... how do I get that background image URL?
The reason why I ask on how to do this in Selenium IDE is because in my company we use it.
I am still googling and since I am not very proficient at JS, I could easily be missing a simple solution!
here's a quick pointer
You'll need to use storeEval to run some js and store the value, so look at the Selenium IDE docs for that
Then the js will be something like this...
getComputedStyle(document.getElementById('hireme'),'').getPropertyValue('background-image');
if you run the snippet above, in the console on this page you should get something like this...
"url(http://careerscdn.sstatic.net/careers/gethired/img/careers2-ad-header-so-crop.png)"
Which will hopefully be good enough for any asserts you want to make
You'll need to replace the document.getElementById('hireme') with document.getElementsByClassName('rabbit')[0];
Hope this helps, use comments if you need any clarification.
You may also need to add this.browserbot.getCurrentWindow(). before the call to document.getElementById