Let's say I had this:
var app = new Vue({
el: '#app',
data: {
message: Math.random()
}
})
And let's say that I wanted to see what value data.message had been assigned in the JS console. How would I do this?
Superficially it seems like doing console.log(app.data.message) would do the trick but when I try to do that I get a Uncaught TypeError: Cannot read properties of undefined (reading 'message') error. In fact, it turns out that app.data is undefined.
So how can I do this?
Here's a JS fiddle with this code:
https://jsfiddle.net/dfzun3by/4/
That code is based off of https://v2.vuejs.org/v2/guide/?redirect=true#Declarative-Rendering
As a corollary to this question... in some production code that I'm now responsible for we don't have that - we have something more akin to this in a *.vue file:
export default {
data() {
return {
message: Math.random()
}
}
}
I tried to do console.log(app) in the JS console of the page that that corresponds to and got a Uncaught ReferenceError: app is not defined error so how could I do the same thing in the production code?
You can access the root instance from JS console with:
document.getElementById('app').__vue__.message
or
app.$options.data().message
For inspecting vue SFC, it is better to use Vue Devtools.
Sounds like the Vue.js Devtools extension might be beneficial for you, it'll allow you to see the values of all variables that are available to the Vue template (so everything in data).
https://devtools.vuejs.org/guide/installation.html
You can reference that value doing console.log(this.message). If you want to log the value every time it changes, you can create a watcher for the message and include "console.log(this.message)" in there.
watch: {
message() {
console.log(this.message)
}
}
I have set up Vue so that I have a top level AppLayout component which just includes a Navigation Menu component, the router-view and, which uses v-if to optionally display an ErrorDisplay component if the error data item is set. I set this from an err state variable in the Vuex store.
That is where I want to get to. However, I think the problem is more fundamental.
In a lower component, I have a submit function that gets called when I click the submit button. To test error handling I have put
throw new Error('Cannot Submit');
In my Main.js I have
handlers for window.orerror, window.addEventListner, Vue.config.errorhandler, Vue.config.warnhandler
All of these should just call the errHandler function, which just calls an action to update the err variable in the state. The hope being that this will then result in the ErrorDisplay component showing on my top level component.
However, I have console.log statements as the first statement in all the above handlers and in my errHandler function. None of these console.logs are getting executed.
In the Console in Chrome, I am just seeing
[vue warn]: Error in v-on handler: "Error: Cannot Submit"
So it is getting the text from my throw, but none of the error handlers seem to be capturing this?
Vue provides Global configuration config.errorHandler to capture error inside Vue components Globally.
As per Official Docs
Assign a handler for uncaught errors during component to render function and watchers. The handler gets called with the error and the Vue instance.
This is how it can be used:
Vue.config.errorHandler = function (err, vm, info) {
// handle error
// `info` is a Vue-specific error info, e.g. which lifecycle hook
// the error was found in. Only available in 2.2.0+
}
Official docs
Hope this helps!
Did more research and I think someone may have already raised a bug report with Vue for this
PR on Vue
https://github.com/vuejs/vue/pull/5709
So it looks like the problem is that the way that I am trying to test this isn't being caught.
I configured 'i-tab-pane': Tabpane but report error，the code is bellow:
<template>
<div class="page-common">
<i-tabs>
<i-tab-pane label="wx">
content
</i-tab-pane>
</i-tabs>
</div>
</template>
<script>
import {
Tabs,
Tabpane
} from 'iview'
export default{
name:"data-center",
data(){
return {msg: 'hello vue'}
},
components: {
'i-tabs' : Tabs,
'i-tab-pane': Tabpane
}
}
</script>
Error traceback：
[Vue warn]: Unknown custom element: <i-tab-pane> - did you register the component correctly? For recursive components, make sure to provide the "name" option.
found in
---> <DataCenter> at src/views/dc/data-center.vue
<Index> at src/views/index.vue
<App> at src/app.vue
I have tried in the main.js to global configuration：
Vue.component("Tabpane", Tabpane);
but still do not work.
How to resolve this issue?
If you're using a component within a component (e.g. something like this in the Vue DOM):
App
MyComponent
ADifferentComponent
MyComponent
Here the issue is that MyComponent is both the parent and child of itself. This throws Vue into a loop, with each component depending on the other.
There's a few solutions to this:
1. Globally register MyComponent
vue.component("MyComponent", MyComponent)
2. Using beforeCreate
beforeCreate: function () {
this.$options.components.MyComponent = require('./MyComponent.vue').default
}
3. Move the import into a lambda function within the components object
components: {
MyComponent: () => import('./MyComponent.vue')
}
My preference is the third option, it's the simplest tweak and fixes the issue in my case.
More info: Vue.js Official Docs — Handling Edge Cases: Circular References Between Components
Note: if you choose method's 2 or 3, in my instance I had to use this method in both the parent and child components to stop this issue arising.
Since you have applied different name for the components:
components: {
'i-tabs' : Tabs,
'i-tab-pane': Tabpane
}
You also need to have same name while you export: (Check to name in your Tabpane component)
name: 'Tabpane'
From the error, what I can say is you have not defined the name in your component Tabpane. Make sure to verify the name and it should work fine with no error.
Wasted almost one hour, didn't find a solution, so I wanted to contribute =)
In my case, I was importing WRONGLY the component.. like below:
import { MyComponent } from './components/MyComponent'
But the CORRECT is (without curly braces):
import MyComponent from './components/MyComponent'
One of the mistakes is setting components as array instead of object!
This is wrong:
<script>
import ChildComponent from './ChildComponent.vue';
export default {
name: 'ParentComponent',
components: [
ChildComponent
],
props: {
...
}
};
</script>
This is correct:
<script>
import ChildComponent from './ChildComponent.vue';
export default {
name: 'ParentComponent',
components: {
ChildComponent
},
props: {
...
}
};
</script>
Note: for components that use other ("child") components, you must also specify a components field!
For recursive components that are not registered globally, it is essential to use not 'any name', but the EXACTLY same name as your component.
Let me give an example:
<template>
<li>{{tag.name}}
<ul v-if="tag.sub_tags && tag.sub_tags.length">
<app-tag v-for="subTag in tag.sub_tags" v-bind:tag="subTag" v-bind:key="subTag.name"></app-tag>
</ul>
</li>
</template>
<script>
export default {
name: "app-tag", // using EXACTLY this name is essential
components: {
},
props: ['tag'],
}
I had this error as well. I triple checked that names were correct.
However I got this error simply because I was not terminating the script tag.
<template>
<div>
<p>My Form</p>
<PageA></PageA>
</div>
</template>
<script>
import PageA from "./PageA.vue"
export default {
name: "MyForm",
components: {
PageA
}
}
Notice there is no </script> at the end.
So be sure to double check this.
If you have path to the component (which causes a cycle) to index.js, cycle will be begin. If you set path directly to component, cycle will be not. For example:
// WRONG:
import { BaseTable } from #/components/Base'; // link to index.js
// SUCCESS:
import BaseTable from #/components/Base/Table.vue';
I had this error and discovered the issue was because the name of the component was identical to the name of a prop.
import Control from '#/Control.vue';
export default {
name: 'Question',
components: {
Control
},
props: ['Control', 'source'],
I was using file components. I changed the Control.vue to InputControl.vue and this warning disappeared.
The high votes answer is right. You can checkout that you have applied different name for the components. But if the question is still not resolved, you can make sure that you have register the component only once.
components: {
IMContainer,
RightPanel
},
methods: {},
components: {
IMContainer,
RightPanel
}
we always forget that we have register the component before
This is very common error that we face while starting any Project Vue. I spent lot of time to search this error and finally found a Solution.
Suppose i have component that is "table.vue",
i.e components/table.vue
In app.js
Vue.component('mytablecomp', require('./components/table.vue').default);
So in in your index.blade file call component as
<mytablecomp></mytablecomp>
Just you need to keep in mind that your component name is in small not in large or camel case.
Then my above code will surely work for you.
Thanks
We've struggled with this error twice now in our project with different components. Adding name: "MyComponent" (as instructed by the error message) to our imported component did not help. We were pretty sure our casing was correct, as we used what is in the documentation, which worked fine for the other 99% of our components.
This is what finally worked for us, just for those two problematic components:
Instead of this (which, again, works for most of our components):
import MyComponent from '#/components/MyComponent';
export default {
components: {
MyComponent
}
We changed it to ONLY this:
export default {
components: {
MyComponent: () => import('#/components/MyComponent')
}
I can't find the documentation we originally found for this solution, so if anyone has any references, feel free to comment.
If you are using Vue Class Component, to register a component "ComponentToRegister" you can do
import Vue from 'vue'
import Component from 'vue-class-component'
import ComponentToRegister from '#/components/ComponentToRegister.vue'
#Component({
components: {
ComponentToRegister
}
})
export default class HelloWorld extends Vue {}
Adding my scenario. Just in case someone has similar problem and not able to identify ACTUAL issue.
I was using vue splitpanes.
Previously it required only "Splitpanes", in latest version, they made another "Pane" component (as children of splitpanes).
Now thing is, if you don't register "Pane" component in latest version of splitpanes, it was showing error for "Splitpanes". as below.
[Vue warn]: Unknown custom element: <splitpanes> - did you register the component correctly? For recursive components, make sure to provide the "name" option.
In my case it was the order of importing in index.js
/* /components/index.js */
import List from './list.vue';
import ListItem from './list-item.vue';
export {List, ListItem}
and if you use ListItem component inside of List component it will show this error as it is not correctly imported. Make sure that all dependency components are imported first in order.
This is WRONG:
import {
Tabs,
Tabpane
} from 'iview'
This is CORRECT:
import Iview from "iview";
const { Tabs, Tabpane} = Iview;
In my case (quasar and command quasar dev for testing), I just forgot to restart dev Quasar command.
It seemed to me that components was automatically loaded when any change was done. But in this case, I reused component in another page and I got this message.
Make sure that the following are taken care of:
Your import statement & its path
The tag name of your component you specified in the components {....} block
i ran into this problem and below is a different solution. I were export my components as
export default {
MyComponent1,
MyComponent2
}
and I imported like this:
import { MyComponent1, MyComponent2} from '#/index'
export default {
name: 'App',
components: {
MyComponent1,
MyComponent2
},
};
And it gave this error.
The solution is:
Just use export { ... } don't use export default
In my case, i was calling twice the import...
#click="$router.push({ path: 'searcherresult' })"
import SearcherResult from "../views/SearcherResult"; --- ERROR
Cause i call in other component...
The error usually arises when we have used the Component (lets say VText) but it has not been registered in the components declaration of the Parent Component(lets say Component B).
The error is more likely to occur when using components in a recursive manner. For example using tag=VText in an tag, as importing the component in a such case will result in error from Eslint as the component is not directly being used in the template. While not importing the component will cause an error in the console saying the component has not been registered.
In this case, it is a better approach to suppress the ESLinter on registration line of the Component(VText in this case). This suppression is done through writing // eslint-disable-next-line vue/no-unused-components
Example code is below
<template>
<i18n path="AssetDict.Companies" tag="VText">
<template>
<span class="bold-500">Hi This is a text</span>
</template>
</i18n>
</template>
<script>
import { VButton, VIcon, VTooltip, VText } from 'ui/atoms'
export default {
name: 'ComponentB',
components: {
VButton,
VIcon,
CompaniesModifyColumn,
VTooltip,
// eslint-disable-next-line vue/no-unused-components
VText,
},
}
</script>
I just encountered this. Easy solution when you know what to look for.
The child component was the default export in it's file, and I was importing using:
import { child } from './filename.vue'
instead of
import child from './filename.vue'.
What happened to me was I had correctly registered the component in components but I had another components key defined at the bottom of my component, so I had two components definitions and it looked like the latter one overrode the previous one. Removing it made it work.
I encounter same error msg while using webpack to async load vue component.
function loadVMap() {
return import(/* webpackChunkName: "v-map" */ './components/map.vue')
.then(({ default: C }) => {
Vue.component('ol-map',C);
return C;
})
.catch((error) => 'An error occurred while loading the map.vue: '+error);
}
I found that the then function never executed.
so I reg this component out of webpack import
import Map from './components/map.vue'
Vue.component('ol-map',Map);
Then I could gain the detailed error msg which said I used a var which is not imported yet.
I ran into this problem when:
I had components defined twice.
Used component instead of components.
I hope this helps others.
The question has been answered very well by #fredrivett here, but I wanted to add some context for other encountering the Circular Reference error when dealing with variables in general.
This error happens with any exported object not just components.
Exporting a variable from parent and importing it in a nested child:
🌐 EXAMPLE
<script>
// parent
export const FOO = 'foo';
...
</script>
❌ WRONG
<script>
// child
import { FOO } from 'path/to/parent'
export default {
data() {
return {
FOO
}
}
}
</script>
✅ CORRECT
<script>
// child
export default {
data() {
return {
FOO: require('path/to/parent').FOO
}
}
}
</script>
Note: in case you are dealing with objects you might want to create a global state which might serve you better.
I'm curious to know if this approach makes sense or it's an anti pattern.
In my case the child component name was "ABCChildComponent" and I was referring in the HTML as assuming it to work correctly. But, the correct name should be or . Hence, changed the name to "AbcChildComponent" and referring in the HTML works fine.
WRONG WAY :
import completeProfile from "#/components/modals/CompleteProfile";
export default {
components: completeProfile
};
RIGHT WAY :
import completeProfile from "#/components/modals/CompleteProfile";
export default {
components: {completeProfile} // You need to put the component in brackets
};
I would like to use JS Hook as described here. Specially, I want to use the afterEnter hook with an async component.
This is my async component:
Vue.component('example', function(resolve, reject){
let data = {
text: 'test data',
};
$.post('http://example.com', data, function(r){
r = JSON.parse(r);
if( r.success ) {
resolve({
template: r.data,
afterEnter: function(el, done){
console.log('test');
}
});
}
});
});
This is what the ajax call gets from the server, and it's what is passed to the template in r.data.
<transition v-on:after-enter="afterEnter"></transition>
These are the two errors that I get.
[Vue warn]: Property or method "afterEnter" is not defined on the instance but referenced during render. Make sure to declare reactive data properties in the data option.
[Vue warn]: Invalid handler for event "after-enter": got undefined
Is it possible to use JS hooks with async components? And if not, how should I approach this? My objective is to run custom JS after Vue (and/or vue-router) inject the component template onto the page, so that I can initiliaze image sliders and whatnot. It is important that my custom JS fires every time the component is navigated to, and not only on the first load.
Thank you.
That warning means that Vue is looking for (but unable to find) a property or method named "afterEnter", which you reference in your template. You have defined afterEnter in your resolve function as if it is a lifecycle hook, but it needs to be one of your Vue instance's methods.
So, your resolve function should look like this:
resolve({
template: r.data,
methods: {
afterEnter: function(el, done) {
console.log('test');
}
}
});