I am trying to build a component that should update the string using setInterval.
Here is the code of the component.
<script>
export default {
data() {
return {
offers: [
'1!',
'2!',
'3!',
],
current_index: 0,
indexInterval: null,
}
},
created() {
this.updateToastIndex()
},
beforeDestroy() {
clearInterval(this.indexInterval)
},
methods: {
updateToastIndex() {
const indexInterval = setInterval(() => {
this.$nextTick(() => {
if (this.current_index === 2) {
this.current_index = 0
console.log(this.offers[this.current_index], 'changedprev')
} else {
this.current_index = this.current_index + 1
console.log(this.offers[this.current_index], 'changed')
}
})
}, 1000)
this.indexInterval = indexInterval
},
},
}
</script>
<template>
<div>{{ offers[current_index] }}</div>
</template>
I can see the current_index in updateToastIndex function getting updated but current_index in template is not getting updated.
Please suggest some solution
I got this weird thing going on here:
I have this data property in vue
data() {
return {
currentLat: 'intial Lat',
currentLong: 'intial Long',
};
},
mounted() {
this.getCurrentLocation();
},
methods: {
getCurrentLocation() {
navigator.geolocation.getCurrentPosition((position) => {
this.currentLat = position.coords.latitude;
this.currentLong = position.coords.longitude;.
console.log(this.currentLat); this prints 41.2111
});
console.log(this.currentLat); this prints 'intial Lat'
},
},
this.currentLat not set in the mount
I dont understand what's happing here! it's so weird!
Here is an example of converting to a promise and using async/await:
async getCurrentLocation() {
const position = await new Promise(resolve => {
navigator.geolocation.getCurrentPosition(position => resolve(position))
});
this.currentLat = position.coords.latitude;
this.currentLong = position.coords.longitude;
console.log(this.currentLat); // shouldn't print initial value
},
Your code is valid, the callback arrow function is asynchronous (it's not executed immediately) and the call of console.log(this.currentLat); is synchronous which makes it to be executed before the callback context, the property is properly if you use it inside the template it will work fine
Set the values in a callback as follows:
<template>
<div id="app">{{ currentLat }} - {{ currentLong }}</div>
</template>
<script>
export default {
data() {
return {
currentLat: "intial Lat",
currentLong: "intial Long",
};
},
mounted() {
this.getCurrentLocation();
},
methods: {
getCurrentLocation() {
navigator.geolocation.getCurrentPosition(this.setCoordinates);
},
setCoordinates(position) {
this.currentLat = position.coords.latitude;
this.currentLong = position.coords.longitude;
},
},
};
</script>
I have a simple input box in a Vue template and I would like to use debounce more or less like this:
<input type="text" v-model="filterKey" debounce="500">
However the debounce property has been deprecated in Vue 2. The recommendation only says: "use v-on:input + 3rd party debounce function".
How do you correctly implement it?
I've tried to implement it using lodash, v-on:input and v-model, but I am wondering if it is possible to do without the extra variable.
In template:
<input type="text" v-on:input="debounceInput" v-model="searchInput">
In script:
data: function () {
return {
searchInput: '',
filterKey: ''
}
},
methods: {
debounceInput: _.debounce(function () {
this.filterKey = this.searchInput;
}, 500)
}
The filterkey is then used later in computed props.
I am using debounce NPM package and implemented like this:
<input #input="debounceInput">
methods: {
debounceInput: debounce(function (e) {
this.$store.dispatch('updateInput', e.target.value)
}, config.debouncers.default)
}
Using lodash and the example in the question, the implementation looks like this:
<input v-on:input="debounceInput">
methods: {
debounceInput: _.debounce(function (e) {
this.filterKey = e.target.value;
}, 500)
}
Option 1: Re-usable, no deps
- Recommended if needed more than once in your project
/helpers.js
export function debounce (fn, delay) {
var timeoutID = null
return function () {
clearTimeout(timeoutID)
var args = arguments
var that = this
timeoutID = setTimeout(function () {
fn.apply(that, args)
}, delay)
}
}
Typescript?
export function debounce<T extends (...args: any[]) => void>(fn: T, delay: number): T {
let timeoutID: number | null = null;
return function (this: any, ...args: any[]) {
clearTimeout(timeoutID);
timeoutID = setTimeout(() => {
fn.apply(this, args);
}, delay);
} as T;
}
Or if using a d.ts:
declare function debounce(fn: (...args: any[]) => void, delay: number): (...args: any[]) => void;
/Component.vue
<script>
import {debounce} from './helpers'
export default {
data () {
return {
input: '',
debouncedInput: ''
}
},
watch: {
input: debounce(function (newVal) {
this.debouncedInput = newVal
}, 500)
}
}
</script>
Codepen
Option 2: In-component, also no deps
- Recommended if using once or in small project
/Component.vue
<template>
<input type="text" v-model="input" />
</template>
<script>
export default {
data: {
timeout: null,
debouncedInput: ''
},
computed: {
input: {
get() {
return this.debouncedInput
},
set(val) {
if (this.timeout) clearTimeout(this.timeout)
this.timeout = setTimeout(() => {
this.debouncedInput = val
}, 300)
}
}
}
}
</script>
Codepen
Assigning debounce in methods can be trouble. So instead of this:
// Bad
methods: {
foo: _.debounce(function(){}, 1000)
}
You may try:
// Good
created () {
this.foo = _.debounce(function(){}, 1000);
}
It becomes an issue if you have multiple instances of a component - similar to the way data should be a function that returns an object. Each instance needs its own debounce function if they are supposed to act independently.
Here's an example of the problem:
Vue.component('counter', {
template: '<div>{{ i }}</div>',
data: function(){
return { i: 0 };
},
methods: {
// DON'T DO THIS
increment: _.debounce(function(){
this.i += 1;
}, 1000)
}
});
new Vue({
el: '#app',
mounted () {
this.$refs.counter1.increment();
this.$refs.counter2.increment();
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.16/vue.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js"></script>
<div id="app">
<div>Both should change from 0 to 1:</div>
<counter ref="counter1"></counter>
<counter ref="counter2"></counter>
</div>
Very simple without lodash
handleScroll: function() {
if (this.timeout)
clearTimeout(this.timeout);
this.timeout = setTimeout(() => {
// your action
}, 200); // delay
}
I had the same problem and here is a solution that works without plugins.
Since <input v-model="xxxx"> is exactly the same as
<input
v-bind:value="xxxx"
v-on:input="xxxx = $event.target.value"
>
(source)
I figured I could set a debounce function on the assigning of xxxx in xxxx = $event.target.value
like this
<input
v-bind:value="xxxx"
v-on:input="debounceSearch($event.target.value)"
>
methods:
debounceSearch(val){
if(search_timeout) clearTimeout(search_timeout);
var that=this;
search_timeout = setTimeout(function() {
that.xxxx = val;
}, 400);
},
If you need a very minimalistic approach to this, I made one (originally forked from vuejs-tips to also support IE) which is available here: https://www.npmjs.com/package/v-debounce
Usage:
<input v-model.lazy="term" v-debounce="delay" placeholder="Search for something" />
Then in your component:
<script>
export default {
name: 'example',
data () {
return {
delay: 1000,
term: '',
}
},
watch: {
term () {
// Do something with search term after it debounced
console.log(`Search term changed to ${this.term}`)
}
},
directives: {
debounce
}
}
</script>
Please note that I posted this answer before the accepted answer. It's not
correct. It's just a step forward from the solution in the
question. I have edited the accepted question to show both the author's implementation and the final implementation I had used.
Based on comments and the linked migration document, I've made a few changes to the code:
In template:
<input type="text" v-on:input="debounceInput" v-model="searchInput">
In script:
watch: {
searchInput: function () {
this.debounceInput();
}
},
And the method that sets the filter key stays the same:
methods: {
debounceInput: _.debounce(function () {
this.filterKey = this.searchInput;
}, 500)
}
This looks like there is one less call (just the v-model, and not the v-on:input).
In case you need to apply a dynamic delay with the lodash's debounce function:
props: {
delay: String
},
data: () => ({
search: null
}),
created () {
this.valueChanged = debounce(function (event) {
// Here you have access to `this`
this.makeAPIrequest(event.target.value)
}.bind(this), this.delay)
},
methods: {
makeAPIrequest (newVal) {
// ...
}
}
And the template:
<template>
//...
<input type="text" v-model="search" #input="valueChanged" />
//...
</template>
NOTE: in the example above I made an example of search input which can call the API with a custom delay which is provided in props
Although pretty much all answers here are already correct, if anyone is in search of a quick solution I have a directive for this.
https://www.npmjs.com/package/vue-lazy-input
It applies to #input and v-model, supports custom components and DOM elements, debounce and throttle.
Vue.use(VueLazyInput)
new Vue({
el: '#app',
data() {
return {
val: 42
}
},
methods:{
onLazyInput(e){
console.log(e.target.value)
}
}
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<script src="https://unpkg.com/lodash/lodash.min.js"></script><!-- dependency -->
<script src="https://unpkg.com/vue-lazy-input#latest"></script>
<div id="app">
<input type="range" v-model="val" #input="onLazyInput" v-lazy-input /> {{val}}
</div>
To create debounced methods you can use computeds, that way they won't be shared across multiple instances of your component:
<template>
<input #input="handleInputDebounced">
<template>
<script>
import debounce from 'lodash.debouce';
export default {
props: {
timeout: {
type: Number,
default: 200,
},
},
methods: {
handleInput(event) {
// input handling logic
},
},
computed: {
handleInputDebounced() {
return debounce(this.handleInput, this.timeout);
},
},
}
</script>
You can make it work with uncontrolled v-model as well:
<template>
<input v-model="debouncedModel">
<template>
<script>
import debounce from 'lodash.debouce';
export default {
props: {
value: String,
timeout: {
type: Number,
default: 200,
},
},
methods: {
updateValue(value) {
this.$emit('input', value);
},
},
computed: {
updateValueDebounced() {
return debounce(this.updateValue, this.timeout);
},
debouncedModel: {
get() { return this.value; },
set(value) { this.updateValueDebounced(value); }
},
},
}
</script>
Here is a vue3 way
...
<input v-model="searchInput">
...
setup(){
const searchInput = ref(null)
const timeoutID = ref(null)
watch(searchInput, (new, old) => {
clearTimeout(timeoutID.value)
timeoutID.value = setTimeout(() => {
//Call function for searching
}, 500) //millisecons before it is run
})
return {...}
}
If you are using Vue you can also use v.model.lazy instead of debounce but remember v.model.lazy will not always work as Vue limits it for custom components.
For custom components you should use :value along with #change.native
<b-input :value="data" #change.native="data = $event.target.value" ></b-input>
1 Short version using arrow function, with default delay value
file: debounce.js in ex: ( import debounce from '../../utils/debounce' )
export default function (callback, delay=300) {
let timeout = null
return (...args) => {
clearTimeout(timeout)
const context = this
timeout = setTimeout(() => callback.apply(context, args), delay)
}
}
2 Mixin option
file: debounceMixin.js
export default {
methods: {
debounce(func, delay=300) {
let debounceTimer;
return function() {
// console.log("debouncing call..");
const context = this;
const args = arguments;
clearTimeout(debounceTimer);
debounceTimer = setTimeout(() => func.apply(context, args), delay);
// console.log("..done");
};
}
}
};
Use in vueComponent:
<script>
import debounceMixin from "../mixins/debounceMixin";
export default {
mixins: [debounceMixin],
data() {
return {
isUserIdValid: false,
};
},
mounted() {
this.isUserIdValid = this.debounce(this.checkUserIdValid, 1000);
},
methods: {
isUserIdValid(id){
// logic
}
}
</script>
another option, example
Vue search input debounce
Here's an example Vue 2 component that demonstrates how to use debounce.
<template>
<div>
<v-btn #click="properDebounceMyMethod">Proper debounce</v-btn>
<v-btn #click="notWorkingDebounceMyMethod">!debounce</v-btn>
<v-btn #click="myMethod">normal call</v-btn>
</div>
</template>
<script lang="ts" >
import { defineComponent } from '#vue/composition-api';
import { debounce } from 'lodash';
export default defineComponent({
name: 'DebounceExample',
created() {
// debounce instance method dynamically on created hook
this.properDebounceMyMethod = debounce(this.properDebounceMyMethod, 500);
},
methods: {
properDebounceMyMethod(){
this.myMethod();
},
notWorkingDebounceMyMethod() {
debounce(this.myMethod, 500);
},
myMethod() {
console.log('hi from my method');
},
}
});
</script>
If you could move the execution of the debounce function into some class method you could use a decorator from the utils-decorators lib (npm install --save utils-decorators):
import {debounce} from 'utils-decorators';
class SomeService {
#debounce(500)
getData(params) {
}
}
I was able to use debounce with very little implementation.
I am using Vue 2.6.14 with boostrap-vue:
Add this pkg to your package.json: https://www.npmjs.com/package/debounce
Add this to main.js:
import { debounce } from "debounce";
Vue.use(debounce);
In my component I have this input:
<b-form-input
debounce="600"
#update="search()"
trim
id="username"
v-model="form.userName"
type="text"
placeholder="Enter username"
required
>
</b-form-input>
All it does is call the search() method and the search method uses the form.userName for perform the search.
<template>
<input type="text" v-model="search" #input="debouncedSearch" />
</template>
<script>
import _ from 'lodash';
export default {
data() {
return {
search: '',
};
},
methods: {
search() {
// Perform the search here
console.log(this.search);
},
},
created() {
this.debouncedSearch = _.debounce(this.search, 1000);
},
};
</script>
public debChannel = debounce((key) => this.remoteMethodChannelName(key), 200)
vue-property-decorator
I'm using Vue CLI and I have these components that has a scroll event on mounted property
comp1.vue
export default{
data(){
showSearchBar : 0
},
mounted(){
const _self = this;
document.querySelectorAll('.page__content').forEach(function(el){
el.onscroll = function() {
if (el.scrollTop >= 200) {
_self.showSearchBar = 1;
}else{
_self.showSearchBar = 0;
}
}
});
}
}
comp2.vue
export default{
data(){
showUsersList : 0
},
mounted(){
const _self = this;
document.querySelectorAll('.page__content').forEach(function(el){
el.onscroll = function() {
if (el.scrollTop >= 200) {
_self.showUsersList = 1;
}else{
_self.showUsersList = 0;
}
}
});
}
}
I know only one event declaration will work if so happens I have multiple scroll handlers on single page, then I have to group them down to a single scroll event so my question is, how do I merge those handlers into one scroll event so to make all of them work? is there a way on this in Vue?
One of the ways you could do this, is by including the logic inside your app.vue, where you also load your <router-view> tag:
We then pass the prop down to the individual pages, where we can use it:
App.vue
<template>
<div class="page__content">
<router-view :scrolled="scrolled"/>
</div>
</template>
<script>
export default{
data(){
scrolled: false
},
mounted(){
// Its better use a vue ref here
document.querySelectorAll('.page__content').forEach((el) => {
el.onscroll = () => {
if (el.scrollTop >= 200) {
this.scrolled = true;
} else {
this.scrolled = false;
}
}
});
}
}
</script>
comp2.vue
export default{
props: {
scrolled: {
type: Boolean,
required: true,
},
},
computed: {
showUsersList() {
if(this.scrolled) {
return 1;
} else {
return 0;
}
},
},
mounted(){
}
}
I have a collection of Events. These will render in lists according to their status - upcoming/live/previous. Thus the rendering is dependent on the current time. How can I make the computed properties to update/recompute as time goes by?
<template>
<div>
<h2>Upcoming events</h2>
<p v-bind:key="event.name" v-for="event in upcomingEvents">{{ event.name }}</p>
<h2>Live events</h2>
<p v-bind:key="event.name" v-for="event in liveEvents">{{ event.name }}</p>
<h2>Previous events</h2>
<p v-bind:key="event.name" v-for="event in previousEvents">{{ event.name }}</p>
</div>
</template>
<script>
import Event from '../Event.js'
export default {
data() {
return {
events: []
}
},
computed: {
upcomingEvents() {
return this.events.filter(event => event.isUpcoming())
},
liveEvents() {
return this.events.filter(event => event.isLive())
},
previousEvents() {
return this.events.filter(event => event.isPrevious())
},
},
mounted() {
// this.events are populated here
}
}
</script>
You can declare a time-dependent data variable and use setInterval() to update it:
data() {
return {
events: [],
now: Date.now()
}
},
created() {
var self = this
setInterval(function () {
self.now = Date.now()
}, 1000)
},
computed: {
upcomingEvents() {
return this.events.filter(event => event.isUpcoming(this.now))
},
liveEvents() {
return this.events.filter(event => event.isLive(this.now))
},
previousEvents() {
return this.events.filter(event => event.isPrevious(this.now))
}
}
Note that you need to use now in computed properties to make them update.
One possibility for your case is $forceUpdate(). However, it should be note that it will work specifically for your case because you're NOT using child components.
If you were to use child components, you would then need to use slots within the parent component and insert the children within their respective slots.
So, for example, you could do:
created() {
setInterval(() => {
this.$forceUpdate()
}, 5000)
}
Which will cause the entire component to re-render. This may or may not be the desirable interaction you're looking for.
You could create a time variable that you update every second then use this variable in your computed properties.
new Vue({
el: "#app",
data: {
time: ''
},
computed: {
computedValue: function(){
return this.time;
}
},
mounted: function(){
var app = this;
setInterval(function(){
app.time = parseInt(new Date().getTime() / 1000);
}, 1000);
}
})
https://jsfiddle.net/ecwnvudz/