I've created a backend and am now trying to build a frontend, using it. I'm very new to Vue.js and am having a hard time telling it to do what I want; probably because of missing some basic concepts. Hopefully someone can point me in the right direction.
The App.vue groups following components: Header, main section (routed), footer and a modal login dialog.
The issue I'm trying to solve is to display the modal login dialog when clicking the Login button (which lives in the header component); currently, nothing besides the messages being logged happens.
For this I've created an event bus and am firing an event:
export default {
name: 'SppdTeamTunerHeader',
methods: {
emitShowLoginDialogEvent () {
EventBus.$emit('ShowLoginDialog', true)
}
}
}
Emitting the event works as I can see in the Vue DevTools for Chrome.
Here's the complete code of App.vue:
<template>
<div id="app">
<SppdTeamTunerHeader/>
<router-view></router-view>
<SppdTeamTunerFooter/>
<LoginDialogModal
v-show="isLoginDialogVisible"
/>
</div>
</template>
<script>
import SppdTeamTunerHeader from '#/components/TheHeader'
import SppdTeamTunerFooter from '#/components/TheFooter'
import LoginDialogModal from '#/components/LoginDialogModal'
import { EventBus } from '#/common/EventBus'
export default {
name: 'App',
components: {
SppdTeamTunerHeader,
SppdTeamTunerFooter,
LoginDialogModal
},
data: function () {
return {
isLoginDialogVisible: false
}
},
mounted () {
EventBus.$on('ShowLoginDialog', function (isVisible) {
console.log('Setting ShowLoginDialog isVisible=' + isVisible + '. isLoginDialogVisible=' + this.isLoginDialogVisible)
if (isVisible) {
this.isLoginDialogVisible = true
} else {
this.isLoginDialogVisible = false
}
console.log('Finished setting isLoginDialogVisible=' + this.isLoginDialogVisible)
})
},
destroyed () {
EventBus.$off('ShowLoginDialog')
}
}
</script>
When checking the console, following is being printed when clicking the login button:
Setting ShowLoginDialog isVisible=true. isLoginDialogVisible=undefined
Finished setting isLoginDialogVisible=true
The value logged for isLoginDialogVisible can't come from the variable defined in the data function as it prints undefined, whereas it has been defined as false (I guess that's my main problem).
I've read quite a few articles about the subject, e.g:
https://codingexplained.com/coding/front-end/vue-js/why-components-data-properties-must-be-functions
https://v2.vuejs.org/v2/guide/instance.html#Data-and-Methods
The modal dialog example I've based the implementation comes from here: https://alligator.io/vuejs/vue-modal-component/
This is happening because you are not using an Arrow function. Instead of a plain function, use arrow function like this:
mounted () {
// Note the use of arrow function.
EventBus.$on('ShowLoginDialog', (isVisible) => {
// .. All your code
})
}
If you use plain function function () {}, then this pointer is not accessible within inner function. Arrow function will lexically bind this pointer to mounted() function's this context. So use an arrow function i.e. () => {};
Note: If you insist on using plain old function syntax then use closure variable to keep track of this pointer:
mounted () {
// Assign this pointer to some closure variable
const vm = this;
EventBus.$on('ShowLoginDialog', function (isVisible) {
console.log('Setting ShowLoginDialog isVisible=' + isVisible + '. isLoginDialogVisible=' + vm.isLoginDialogVisible)
if (isVisible) {
vm.isLoginDialogVisible = true
} else {
vm.isLoginDialogVisible = false
}
console.log('Finished setting isLoginDialogVisible=' + vm.isLoginDialogVisible)
})
}
This has nothing to do with Vue.js. It is a typical JavaScript behavior.
I believe your listener for the EventBus events needs to be accessible to App. Right now EventBus and App are two separate instances. You could mount the event handler inside App like this:
mounted () {
EventBus.$on('ShowLoginDialog', function (isVisible) {
...
});
Related
So I have implemented Echarts with a Vue application, on one of the charts, I am trying to get the item clicked and pass it back to the parent component that way I can do specific calculations to it.
The 'on click' method works and I can console.log('params') easily, however, trying to reach any other functions outside of it is not possible for some reason...
here is my code...
data() {
return {
myChart: null,
selectedState: {}
}
}.
mounted() {
this.myChart = echarts.init(document.getElementById("geoMap"))
this.myChart.on('click', function(params){
// It will run the console.log with correct info, but the
// method is not reachable...
console.log(params)
this.setSelectedState(params)
})
},
// Inside my vue script this is just a method to set the data for now...
methods: {
setSelectedState(params){
this.selectedState = params
},
}
any help would be nice!! thanks!
You're not in the Vue component context when listening to the chart event, so you have to change your callback function to an arrow one to access the component's this :
this.myChart.on('click', params => {
this.setSelectedState(params)
});
methods: {
setSelectedState(params) {
console.log(params);
this.selectedState = params
}
}
By the way, you should use ref instead of getting your div with document.getElementById to attach your chart :
<div ref="geoMap"></div>
this.myChart = echarts.init(this.$refs.geoMap);
First of all, I am a new vuejs developer and my purpose is to get acquainted with Vue, so, not going to use any external plugins or components.
I am writing a simple alert component, which looks like this:
<Alert :show="showAlert" />
I want the show property to return back to false after 2 seconds. How can I do this from inside the component (i.e., not in the page where this component is used). I tried this:
import { computed } from 'vue';
export default {
props: ['show'],
setup(props) {
const shown = computed(() => {
if (props.show) {
setTimeout(() => {
console.log("hiding the alert...")
props.show = false
}, 2000);
}
return props.show.value
})
return { shown }
}
};
the compiler said:
14:15 error Unexpected timed function in computed function vue/no-async-in-computed-properties
16:19 error Unexpected mutation of "show" prop vue/no-mutating-props
My rational is that the delay of alert should be controlled by the alert component (which could be changed by a prop), but not forcing the caller to write some thing like:
function Alert(delay) {
showAlert = true
setTimeout(() => showAlert = false, delay)
}
There are 2 errors.
First vue/no-mutating-props, props are read only so you are not supposed to change it from within the component. It is still possible to change props from outside the component and pass down to it.
For this you should copy the value of props to your data()
data() {
return {
showAlert
}
}
You should be able to update showAlert with no problem.
The second error vue/no-async-in-computed-properties, you cannot write async function inside computed(), so the alternative is to use watch instead.
I have registered 'beforeunload' event on created hook of the component used by routes of vue router.
I want to call this event handler in order to remove user on browser tab close or browser tab refresh or browser close.
On ComponentA
created (){
window.addEventListener('beforeunload', () => {
this.removeUser()
return null
})
}
Smilarly on ComponentB
created (){
window.addEventListener('beforeunload', () => {
this.removeUser()
return null
})
}
And my router.js
{
path: '/staff/call/:session_key',
name: 'Staff Call',
component: ComponentA,
meta: {auth: true}
},
{
path: '/consumer/call/:session_key',
name: 'Consumer Call',
component: ComponentB
},
Here 'beforeunload' event handler is triggered randomly. That is sometimes it get triggered and sometimes not. I count find any pattern when it is triggered and when it is not.
What am I missing here?
Edit
I'd guess the most likely culprit then is exactly what #PatrickSteele said. From MDN:
Note: To combat unwanted pop-ups, some browsers don't display prompts
created in beforeunload event handlers unless the page has been
interacted with; some don't display them at all. For a list of
specific browsers, see the Browser_compatibility section.
I'd say it's likely you're seeing inconsistent behavior because you are sometimes not interacting with the page.
This may be a syntax error. created should be a method
created () {
window.addEventListener('beforeunload', this.removeUser)
},
methods: {
removeUser () {
//remove user here
}
}
A fiddle working: https://jsfiddle.net/e6m6t4kd/3/
It's work for me. while do something before reload or close in
vue.js
created() {
window.onbeforeunload = function(){
return "handle your events or msgs here";
}
}
I had to do some fiddling on the above examples, I believe this is the most robust solution:
let app1 = new Vue({
delimiters: ['[[', ']]'],
el: '#app',
data: {
dirty_form: true,
},
created () {
console.log('created')
window.addEventListener('beforeunload', this.confirm_leaving)
},
methods: {
confirm_leaving (evt) {
if (this.dirty_form) {
const unsaved_changes_warning = "You have unsaved changes. Are you sure you wish to leave?";
evt.returnValue = unsaved_changes_warning;
return unsaved_changes_warning;
};
};
},
});
If you want detect page refresh/change in Vue whenever you press F5 or Ctrl + R, You may need to use Navigation Timing API.
The PerformanceNavigation.type, will tell you how the page was accessed.
created() {
// does the browser support the Navigation Timing API?
if (window.performance) {
console.info("window.performance is supported");
}
// do something based on the navigation type...
if(performance.navigation.type === 1) {
console.info("TYPE_RELOAD");
this.removeUser();
}
}
Not sure why none of the above were fully working for me in vue 3 composition api. Abdullah's answer partially works but he left out how to remove the listener.
setup() {
const doSomething = (e) => {
// do stuff here
return true
}
onBeforeMount(() => {
window.onbeforeunload = handleLeaveWithoutSaving
})
onUnmounted(() => {
window.onbeforeunload = null
})
}
I am using Vuex in my app. I dispatch an action inside the component. I get back the result in then(). I need to assign part of that result to some local variables defined in the Vue component. I am only able to do this if I bind the then() with this. Is there a way to achieve the same without using bind.
Here is my original code, I am talking about the line this.$store.dispatch:
<script>
/* eslint-disable */
import * as d3 from 'd3'
import FlightCard from './FlightCard'
export default {
name: 'AirportLayout',
components: {FlightCard},
props: ['id'],
data () {
return {
cardActivator: null
}
},
methods: {
// show flight card menu
showFlightCard: function (e) {
// debugger
let flight = this.$store.state.demo.find(a => {
return a.flightNr === e.target.id
})
this.$store.dispatch('getFlightCard', {flightNr: flight.flightNr, scheduledDate: flight.scheduledDate}).then(function (){
debugger
// here I want to do something with the response
this.cardActivator = document.getElementById(e.target.id)
console.log('Showing flight card for: ', this.cardActivator)
}.bind(this)) // Using bind, this gets the value of Vue component
}
}
}
</script>
I read the documentation for arrow functions here Arrow functions, it says an arrow function does not create its own this, the this value of the enclosing execution context is used. I assumed that would be the Vue component, and I tried it, but then this value was undefined. So I concluded the execution context must be referring to the then(), am I right? If yes, how could I make this inside then() refer to the Vue component?
Here is my code using arrow functions
<script>
/* eslint-disable */
import * as d3 from 'd3'
import FlightCard from './FlightCard'
export default {
name: 'AirportLayout',
components: {FlightCard},
props: ['id'],
data () {
return {
cardActivator: null
}
},
methods: {
// show flight card menu
showFlightCard: function (e) {
// debugger
let flight = this.$store.state.demo.find(a => {
return a.flightNr === e.target.id
})
this.$store.dispatch('getFlightCard', {flightNr: flight.flightNr, scheduledDate: flight.scheduledDate}).then(r => {
debugger
// here I want to do something with the response
this.cardActivator = document.getElementById(e.target.id)
console.log('Showing flight card for: ', this.cardActivator)
}) // here the value for this is undefined
}
}
}
</script>
I have a login modal that I activate by setting .is-active to it. For this, I have a method like this:
methods: {
toggleModal: function (event) {
this.isActive = !this.isActive
}
}
that I run onclick. Depending on the boolean value of isActive, my modal gets the class .is-active.
Thing is, in my modal I have a button that takes the user to a new view which means it's rendering a new component, with this code:
<router-link class="control" #click="toggleModal()" to="/register">
As you can see, it's routing to /register. Before doing this, I need to run toggleModal() so that the modal gets closed. Right now it's routing without running the method which means that the new view has my modal overlay which is... not optimal.
Is there any good way to do this in Vue? Could I maybe create a method, that first calls toggleModal(), and then routes from the method?
Thanks.
I would define a method that calls toggleModal first, then navigates. Like so:
methods: {
navigateAway () {
this.isActive = !this.isActive
this.$router.push('/register')
}
}
You don't need the event argument unless you intend on capturing more data from the event or event target. You could also wrap the router push in a setTimeout if you so desire, for perhaps cleaner looking view changes.
methods: {
navigateAway () {
let vm = this
vm.isActive = !vm.isActive
setTimeout(function () {
vm.$router.push('/register')
}, 50)
}
}
Of course, there are hooks that you can use from vue-router that make this easy. Example (assuming you're using single file components and Vue.js 2.x):
export default {
data () {
return {
isActive: false
}
},
beforeRouteLeave (to, from, next) {
this.isActive = false // I assume that you would not want to leave it open upon navigating away
next()
}
}
Link to vue router hooks: https://router.vuejs.org/en/advanced/navigation-guards.html