I am encountering this strange behavior in my code in Vue 2
What I am trying to achieve here is when I clicked on one of the checkbox, other checkbox(es) are checked as well. I only want the selected checkbox to be checked only. Is there a way to do so?
this is my component
<div v-for="(item,index) in api[0].choice" :key="index">
<input type="checkbox" #change="detect" v-model="option[index].checked">
<label>{{item}}</label>
</div>
data(){}
option: null,
mounted(){}
this.option = Array(this.api[0].choice.length).fill({checked: false})
Array.prototype.fill() passes a reference and not a new instance. So essentially all of your items inside of your array are mapped together. Thus when index n changes so do all the other values.
The easiest way to fix this, is to fill with undefined, by not passing an argument to fill, and then update the array, mapping the same object over and over again. Thus creating new instances of the object, instead of referencing the original object.
this.option = Array(5)
.fill()
.map((x) => ({ checked: false }));
Example on codesandbox
If you are expecting to have really large arrays .map() will be inefficient. Use a for loop instead
this.option = new Array(5);
for (let i = 0; i < 5; i++) {
this.option[i] = { checked: false };
}
Related
I want to keep the value of a variable identical with the content of a textarea.
I don't want to use v-bind or v-model, because I have already bound the textarea with another value.
This is a notebook app, and the textarea is used to display the content of a note, so it has been bound using v-bind with a note object, like
<textarea cols="30" rows="3" v-bind:value="note"></textarea>
Now, I want to add the "edit note" functionality. So when the content of the textarea changes, I want to store its value into a variable, and when the "submit" button is clicked, I pass the value of the variable, which contains the new content of the note, to backend to update the note.
My question is, how to store the textarea's content into the variable after each time the content changes?
I think I cannot use v-model because this way the note will be changed right after the content of the textarea is modified (though not sent to backend), but this is not what I want. What I want is the note to be changed only after the "submit" button is clicked. Thus, I cannot use v-model
Should I use v-on:change? If so, how to get the content of the textarea?
Like,
<textarea v-on:change="updateTheVariable(I need to get the content of the textarea here)"> ... </textarea>
methods: {
updateTheVariable(content of the textarea) {
this.variable = content of the textarea
}
}
Thanks
I'm assuming this thing only shows up when you click some kind of edit button which is why you don't want to alter note so try something like this instead
<button type="button" v-if="!editMode" #click="editNote">Edit</button>
<form v-if="editMode" #submit="handleSubmit">
<fieldset :disabled="saving">
<textarea v-model="editingNote"></textarea>
<button type="submit">Edit</button>
</fieldset>
</form>
export default {
data: () => ({
note: 'whatever', // maybe it's a prop, maybe assigned later, doesn't matter
editMode: false,
editingNote: null, // this will be used to bind the edited value
saving: false
}),
methods: {
editNote () {
this.editingNote = this.note
this.editMode = true
this.saving = false
},
async handleSubmit () {
this.saving = true // disables form inputs and buttons
await axios.post('/notes/update', { note: this.editingNote}) // just an example
this.note = this.editingNote // or maybe use data from the response ¯\_(ツ)_/¯
// or if it's a prop, this.$emit('updated', this.editingNote)
this.editMode = false
}
}
}
As #Phil indicated in a deleted post, the right way to do it is
<textarea #input="updateTheVariable($event.target.value)"></textarea>
.
.
.
methods:{
updateTheVariable(value){
this.variable = value
}
}
I'm creating a list of (thumbnail) 2 images, and #click each image should be expanded to max-width, by adding said class ('max-w-full') to the classes. The class is added by setting the array entry with the same index nr. as the image (imgclicked[0], imgclicked[1]) in the list to 1.
data:() {
imgclicked=[0,0], //by default both are set to 'small'/not 'max-w-full'
},
the template part looks like this:
<template v-for="(image,index) in images>
<a #click="zoomImgClicked(index)">
<img :src="image.filename" :class={'max-w-full' : imgclicked[index]==1,'w-12' : imgclicked[index]==0}">
</a> // using this.imgclicked[index] gives me the error 'this.imgclicked[0] is undefined'
</template>
on click the method zoomImgClicked() ist launched:
zoomImgClicked: function(i){
if(this.imgclicked[i]==0){
this.imgclicked[i]=1
}else{
this.imgclicked[i]=0
}
},
But this is not working. If I open the vue console and change the values of imgclicked[0] manually from 0 to 1 it works (images ae being resized). Also I see the method doing it's work, when logging in the console, the values are changed from 0 to 1 and vice versa. But it's not reflected on the page #click.
Why is that?
Please read Change Detection Caveats in the Vue docs.
Vue cannot detect the following changes to an array:
When you directly set an item with the index, e.g. vm.items[indexOfItem] = newValue
When you modify the length of the array, e.g. vm.items.length = newLength
You should use the $set method for this:
this.$set(this.imgclicked, i, 1)
try with array syntax:
<img
:src="image.filename"
:class="[
{
'max-w-full': imgclicked[index]==1,
'w-12': imgclicked[index]==0
},
'static class if need'
]"
>
I have a list of objects that can be updated from the database.
So, when I load the list, objects have only id and name.
When I click on an object I load other fields that can be of any length - that's why I don't load them with the objects in the list.
I found that when I update an object it can be difficult to keep reactivity https://v2.vuejs.org/v2/guide/reactivity.html so I need to find some workaround.
this code works almost okay:
axios.get('/api/news', item.id).then(function(response){
if (response){
Object.assign(item, response.data.item);
}
});
But the problem is the fields that have not been presented from the beginning is not 100% reactive anymore. What is going on is a new field has been updated reactively only when I change another, previous one. So, if I show 2 text field with old and new properties, if I change the second property, the field will not be updated until I change the first one.
I got item object from the component:
data () {
return {
items: [],
}
},
and
<div v-for="item in items" #click="selectItem(item)" >
<span>{{item.name}}</span>
</div>
Then item's been passed to the function selectItem.
What is the proper pattern to load new fields and keep them reactive? (NB: it's not the case when I can assign field by field - I want to reuse the same code no matter which object it is, so I need so the solution for updating an object at a time without listing all new fields.)
Note. This code works inside the component.
Completely revised post: Ok, the example you give uses an array, which has its own caveats, in particular that you can't directly set values like vm.items[indexOfItem] = newValue and have it react.
So you have to use Vue.set with the array as the first argument and the index as the second. Here's an example that adds a name property to object items and then uses Vue.set to set the item to a new object created by Object.assign.
new Vue({
el: '#app',
data: {
items: [{
id: 1,
other: 'data'
}, {
id: 2,
other: 'thingy'
}]
},
methods: {
selectItem(parent, key) {
const newObj = Object.assign({}, parent[key], {
name: 'some new name'
});
Vue.set(parent, key, newObj);
setTimeout(() => {parent[key].name = 'Look, reactive!';}, 1500);
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
<div v-for="item, index in items" #click="selectItem(items, index)">
<span>{{item.name || 'empty'}}</span>
</div>
<pre>
{{JSON.stringify(items, null, 2)}}
</pre>
</div>
Have a look at Change-Detection-Caveats Vue cannot detect property addition or deletion if you use "normal assign" methods.
You must use Vue.set(object, key, value)
Try something like the following:
axios.get('/api/news', item.id).then(function(response){
if (response){
let item = {}
Vue.set(item, 'data', response.data.item)
}
});
Than item.data would than be reactiv.
Can simply use Vue.set to update this.item reactively
axios.get('/api/news', item.id).then(function(response){
if (response){
this.$set(this, "item", response.data.item);
}
});
I am using vue-paginate in my app and I've noticed that once my array is empty, refreshing its value to an array with contents does not display.
<paginate
name="recipes"
:list="recipes"
:per="16"
class="p-0"
>
<transition-group name="zoom">
<div v-for="recipe in paginated('recipes')" :key="recipe.id">
<recipe class=""
:recipe="recipe"
:ref="recipe.id"
></recipe>
</div>
</transition-group>
</paginate>
This is how things get displayed, and my recipe array changes depending on a search. If I type in "b" into my search, results for banana, and bbq would show. If I typed "ba" the result for bbq is removed, and once I backspace the search to "b" it would re-appear as expected.
If I type "bx" every result is removed and when I backspace the search to "b", no results re-appear.
Any idea why this might happen?
UPDATE
When I inspect the component in chrome I see:
currentPage:-1
pageItemsCount:"-15-0 of 222"
Even though the list prop is:
list:Array[222]
Paginate needs a key in order to know when to re-render after the collection it's looking at reaches a length of zero. If you add a key to the paginate element, things should function as expected.
<paginate
name="recipes"
:list="recipes"
:per="16"
class="p-0"
:key="recipes ? recipes.length : 0" // You need some key that will update when the filtered result updates
>
See "Filtering the paginated list" is not working on vue-paginate node for a slightly more in depth answer.
I found a hacky workaround that fixed it for my app. First, I added a ref to my <paginate></paginate> component ref="paginator". Then I created a computed property:
emptyArray () {
return store.state.recipes.length == 0
}
then I created a watcher that looks for a change from length == 0 to length != 0:
watch: {
emptyArray: function(newVal, oldVal) {
if ( newVal === false && oldVal === true ) {
setTimeout(() => {
if (this.$refs.paginator) {
this.$refs.paginator.goToPage(page)
}
}, 100)
}
}
}
The timeout was necessary otherwise the component thought there was no page 1.
Using :key in the element has certain bugs. It will not work properly if you have multiple search on the table. In that case input will lose focus by typing single character. Here is the better alternative:
computed:{
searchFilter() {
if(this.search){
//Your Search condition
}
}
},
watch:{
searchFilter(newVal,oldVal){
if ( newVal.length !==0 && oldVal.length ===0 ) {
setTimeout(() => {
if (this.$refs.paginator) {
this.$refs.paginator[0].goToPage(1)
}
}, 50)
}
}
},
Good evening,
My problem is this: I have a loop that displays simple divs.
I have a method that specifies the dimensiosn of my div (mandatory in my case). However, when I call the method a second time by changing the sizes of the divs, it does not work because there is no re-render.
To overcome this, I generate a guid on my: key of v-for with a variable such as:
<div v-for="task in tasks" :key="task.id + guid()">...blabla...</div>
Is it possible to generate this code directly during the loop to avoid concatenation?
<div v-for="(task, maVar=guid()) in tasks" :key="maVar">...blabla...</div>
PS : code for guid() method :
guid() {
return ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, c =>
(c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16))
}
Thanks
You could create a computed property that returns an array of task with a guid added, or if you want to leave tasks untouched, return an object containing each task plus a guid,
computed: {
tasksWithGuid: function() {
return this.tasks.map(task => { return {task, key: task.id + guid() } })
}
}
<div v-for="taskWithGuid in tasksWithGuid" :key="taskWithGuid.key">
{{taskWithGuid.task.someProperty}}
</div>
There is a simpler, more concise technique shown below. It avoids polluting the iterated object with a redundant property. It can be used when there is no unique property in the objects you iterate over.
First in your viewmodel add the method to generate a random number (e.g. with Lodash random)
var random = require('lodash.random');
methods: {
random() {
return random(1000);
}
}
Then in your template reveal the index in v-for and randomize it in v-bind:key with your random() method from the viewmodel by concatenation.
<div v-for="(task, index) in tasks" v-bind:key="index + random()">
// Some markup
</div>
This is as clean as easy.
However note this approach would force redrawing each item in the list instead of replacing only items that differ. This will reset previously drawn state (if any) for unchanged items.
I do like this
function randomKey() {
return (new Date()).getTime() + Math.floor(Math.random() * 10000).toString()
}