I have created vue and electron app using #vue/cli-service 4.2 in that I am facing a issue of optional chaining.
I can't use ? for validating the condition like (#babel/plugin-proposal-optional-chaining)
eg. a?.b?.c its means it check weather a exist then check for b otherwise
return false same as template expression in angular.
Any one have idea how to configure optional chaining in vuejs.
One quick update is that Vue 3 comes bundled with support for optional chaining.
To test you can try compiling the below Vue component code.
<template>
<div id="app" v-if="user?.username">
#{{ user?.username }} - {{ fullName }} <strong>Followers: </strong>
{{ followers }}
<button style="align-self: center" #click="followUser">Follow</button>
</div>
</template>
<script lang="ts">
import { defineComponent } from 'vue'
export default defineComponent({
name: 'App',
props: {
test: Object
},
data() {
return {
followers: 0,
user: {
id: 1,
test: {},
username: '_sethAkash',
firstName: undefined,
lastName: 'Seth',
email: 'sethakash007#gmail.com',
isAdmin: true
}
}
},
computed: {
fullName(): string {
//
return `${this?.test?.firstName} ${this?.user?.lastName}`
}
},
methods: {
followUser: function () {
this.followers += 1
}
},
watch: {
followers(newFollowerCount, oldFollowerCount) {
if (oldFollowerCount < newFollowerCount) {
console.log(`${this?.user?.username} has gained a follower!`)
}
}
},
mounted() {
this.followUser()
}
})
</script>
Try vue-template-babel-compiler
It uses Babel to enable Optional Chaining(?.), Nullish Coalescing(??) and many new ES syntax for Vue.js SFC.
Github Repo: vue-template-babel-compiler
DEMO
Usage
1. Install
npm install vue-template-babel-compiler --save-dev
2. Config
1. Vue-CLI
DEMO project for Vue-CLI
// vue.config.js
module.exports = {
chainWebpack: config => {
config.module
.rule('vue')
.use('vue-loader')
.tap(options => {
options.compiler = require('vue-template-babel-compiler')
return options
})
}
}
2. Nuxt.js
DEMO project for Nuxt.js
// nuxt.config.js
export default {
// Build Configuration: https://go.nuxtjs.dev/config-build
build: {
loaders: {
vue: {
compiler: require('vue-template-babel-compiler')
}
},
},
// ...
}
Please refer to REAMDE for detail usage
Support for Vue-CLI, Nuxt.js, Webpack , any environment use vue-loader v15+.
According to this comment on an issue here
You could create a global mixin and use the eval function to evaluate the expression.
Example:
Vue.mixin({
methods: {
$evaluate: param => eval('this.'+param)
}
});
In the template:
<template>
<p>{{ $evaluate('user?.name') }}</p>
</template>
They also added that it might not be perfect:
Although it's still no substitute for the real operator, especially if you have many occurrences of it
Edit
As stated above, using eval may bring some unintended problems, I suggest you use a computed property instead.
In the SFC:
<template>
<p>{{ userName }}</p>
</template>
<script>
export default {
data(){
return {
user: {
firstName: 'Bran'
}
}
},
computed: {
userName(){
return this.user?.firstName
}
}
}
</script>
/*
* Where to use: Use in vue templates to determine deeply nested undefined/null values
* How to use: Instead of writing parent?.child?.child2 you can write
* isAvailable(parent, 'child.child2')
* #author Smit Patel
* #params {Object} parent
* {String} child
* #return {Boolean} True if all the nested properties exist
*/
export default function isAvailable(parent, child) {
try {
const childArray = String(child).split('.');
let evaluted = parent;
childArray.forEach((x) => {
evaluted = evaluted[x];
});
return !!evaluted;
} catch {
return false;
}
}
Use :
<template>
<div>
<span :v-if="isAvailable(data, 'user.group.name')">
{{ data.user.group.name }}
<span/>
</div>
</template>
<script>
import isAvailable from 'file/path';
export default {
methods: { isAvailable }
}
</script>
This doesn't work exactly the same but I think, in this context, it may be event better for most cases.
I used Proxy for the magic method effect. You just need to call the nullsafe method of an object and from there on, just use normal chaining.
In some versions of VueJs you can't specify a default value. It perceives our null safe value as an object (for good reason) and JSON.stringify it, bypassing the toString method. I could override toJSON method but you can't return the string output. It still encodes your return value to JSON. So you end up with your string in quotes.
const isProxy = Symbol("isProxy");
Object.defineProperty(Object.prototype, 'nullsafe', {
enumarable: false,
writable: false,
value: function(defaultValue, maxDepth = 100) {
let treat = function(unsafe, depth = 0) {
if (depth > maxDepth || (unsafe && unsafe.isProxy)) {
return unsafe;
}
let isNullish = unsafe === null || unsafe === undefined;
let isObject = typeof unsafe === "object";
let handler = {
get: function(target, prop) {
if (prop === "valueOf") {
return target[prop];
} else if (typeof prop === "symbol") {
return prop === isProxy ? true : target[prop];
} else {
return treat(target[prop], depth + 1);
}
}
};
let stringify = function() {
return defaultValue || '';
};
let dummy = {
toString: stringify,
includes: function() {
return false;
},
indexOf: function() {
return -1;
},
valueOf: function() {
return unsafe;
}
};
return (isNullish || isObject) ? (new Proxy(unsafe || dummy, handler)) : unsafe;
};
return treat(this);
}
});
new Vue({
el: '#app',
data: {
yoMama: {
a: 1
}.nullsafe('xx'),
yoyoMa: {
b: 1
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
{{ yoMama.yoyoMa.yoMama.yoyoMa.yoMama }}
<hr> {{ yoyoMa.nullsafe('yy').yoMama.yoyoMa.yoMama.yoyoMa }}
</div>
After search many possibilities, I maked one function to help me.
Make one js file to save the helper function and export it
const propCheck = function (obj = {}, properties = ""){
const levels = properties.split(".");
let objProperty = Object.assign({}, obj);
for ( let level of levels){
objProperty = objProperty[level];
if(!objProperty)
return false;
}
return true;
}
export default propCheck;
And install this function for globally in the Vue instance
Vue.prototype.$propCheck = propCheck;
After use in your template
<span>{{$propCheck(person, "name")}}</span>
or
<span>{{$propCheck(person, "contatcs.0.address")}}</span>
or
<span>{{$propCheck(person, "addres.street")}}</span>
Use getSafe() method way for template and js files :)
<template><div>
{{getSafe(() => obj.foo.bar)}} <!-- returns 'baz' -->
{{getSafe(() => obj.foo.doesNotExist)}} <!-- returns undefined -->
</div></template>
<script>
export default {
data() {
return {obj: {foo: {bar: 'baz'}}};
},
methods: {getSafe},
};
function getSafe(fn) {
try { return fn(); }
catch (e) {}
}
</script>
July 2022 Update:
It works with Vue 2.7 (https://blog.vuejs.org/posts/vue-2-7-naruto.html)
2.7 also supports using ESNext syntax in template expressions.
You can use loadash's get method in this case:
_.get(object, path, [defaultValue])
Gets the value at path of object. If the resolved value is undefined, the defaultValue is returned in its place.
https://lodash.com/docs/4.17.15#get
var object = { 'a': [{ 'b': { 'c': 3 } }] };
_.get(object, 'a[0].b.c');
// => 3
_.get(object, 'a.b.c', 'default');
// => 'default'
In my nuxtjs app static folder I have a file called data.json
in my component I use this data like so
<script>
import data from '~/static/data.json';
export default {
data ({ params }) {
return {
data
}
}
}
</script>
now I have a method that will basically take values from that data and create a little counting up animation like so
methods: {
countUp(value) {
for (let i = 0; i <= value; i++) {
setTimeout(() => {
return i;
}, 100);
}
}
}
and in my template I am calling it like so
<template>
<div>
<p>{{countUp(data.number)}}</p>
</div>
</template>
now the expected result is for the number to quickly change from 0 to the value but nothing is being printed on the dom if I inspect the html element its empty??
What am I doing wrong??
setTimeout doesn't work the way you think it does:
You can't return a value from inside the callback function; nothing is being returned from the countUp method.
The call to setTimeout doesn't block, meaning it will return immediately after being called and the callback function passed to it is scheduled for execution asynchronously after the timeout has passed. So every setTimeout call in the for loop will be executed all at once after 100 ms instead of staggered.
You will need to store the current counter value as data on the component so Vue knows to rerender when its value is changed.
The simplest example I can provide follows, but you might want to encapsulate the logic in a separate reusable component.
const value = 50
new Vue({
el: '#app',
data: {
counter: 0,
},
methods: {
countUp() {
const interval = setInterval(() => {
this.counter++
if (this.counter >= value) {
clearInterval(interval)
}
}, 100)
}
}
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
<button #click="countUp">Count Up</button>
{{ counter }}
</div>
I have a basic CRUD rails 5.2 API with a Story model. I am building a Vuejs front end to consume it. Currently, The index view at /stories successfully pulls in data from the server. I can also add stories to the database via NewStory.vue at stories/new. I am trying now to show a single story on a page at stories/:id. The api server currently shows the single result I need at v1/stories/:id.
here is what I have at services/Api.js:
import axios from 'axios'
export default() => {
return axios.create({
baseURL: `http://localhost:3000/v1`
})
}
in StoriesService.js:
import Api from '#/services/Api'
export default {
fetchStories () {
return Api().get('stories')
},
addStory (params) {
return Api().post('stories', params)
},
getStory (params) {
return Api().get('/stories/1')
}
}
in ViewStory.vue:
<template>
<div class="stories">
<h1>Story</h1>
<div v-if="story" class="table-wrap">
<div>
<router-link v-bind:to="{ name: 'NewStory' }" class="">Add
Story</router-link>
</div>
<p>Title: {{story.attributes.title}}</p>
<p>Overview: {{story.attributes.description}}</p>
</div>
<div v-else>
The story with id:{{params}} does not exist <br><br>
<!-- <router-link v-bind:to="{ name: 'NewStory' }"
class="add_story_link">Add Story</router-link> -->
</div>
</div>
</template>
<script>
import StoriesService from '#/services/StoriesService'
export default {
name: 'story',
data () {
return {
title: '',
description: ''
}
},
mounted () {
this.getStory()
},
methods: {
async getStory (params) {
const response = await StoriesService.getStory(params)
this.story = response.data
console.log(this.story)
}
}
}
</script>
With the id of the record hard coded, in the Network tab, I see the request being made to the api and the correct record being retrieved.
However, if I change the getStory call to return Api().get('/stories/', params) I get a 304 response and can't retrieve data.
My question is how to get StoriesService.js to return localhost:3000/v1/stories/params.id, where params.id is the id of the story referenced in the url.
Currently you are not passing in any params to getStory, so you need to get them from the this.$route.params
async getStory () {
const response = await StoriesService.getStory(this.$route.params)
this.story = response.data
console.log(this.story)
}
Beside that axios only supports query string parameters so if your url looks like /stories/someId then you need to build it yourself in getStory:
getStory (params) {
return Api().get(`/stories/${params.id}`)
}
Additionally your data object is missing the story property:
data () {
return {
story: null,
title: '',
description: ''
}
},
I have created a component which has a function which makes external API calls and then fills an array. I used created() life hook to run the function for the 1st time. I am passing a variable from the parent component into this component and then based upon this variable change I want the function to run again.
How do I achieve this.
Attaching my code below
<template>
<div>
<p>{{ data_to_show_on_mainpage }}</p>
</div>
</template>
<script>
import axios from 'axios'
export default {
name: 'GetCategoryItemsAndDisplayOne',
props: ['categoriesfordisplay','ismainpage', 'catalogselected'],
data(){
return {
IsMainPage_1 : "",
data_to_show_on_mainpage : [],
}
},
watch: {
catalogselected: function(){
this.GetItemsToShowonMainPage()
}
},
methods:{
changevalue(){
console.log("i am reducing it to emplty after change of catalog")
this.IsMainPage_1 = this.catalogselected
this.data_to_show_on_mainpage = []
},
CatlogService(catlog_name,category,gender,mainpage){
let url = "http://localhost:5000/xyz/" + (this.catalogselected).replace(/'/g,"%27") +"/api/"+ (gender) + "/catalogvis/" + (category) +"/items"
console.log(encodeURI(url))
axios.get(encodeURI(url)).then((resp)=>{
this.data_to_show_on_mainpage.push(resp.data.response.Results.results[0])
})
.catch(err => {
console.log("we got an error the url is " + url)
console.log(err);
})
},
GetItemsToShowonMainPage(){
this.changevalue()
if(this.categoriesfordisplay.men_for_display.length>0){
for(let i =0;i<this.categoriesfordisplay.men_for_display.length;i++){
let category = this.categoriesfordisplay.men_for_display[i].replace(/"/g,"%27");
this.CatlogService(this.catalogselected,category,'men',this.ismainpage)
}
}
if(this.categoriesfordisplay.women_for_display.length>0){
for(let i = 0;i<this.categoriesfordisplay.women_for_display.length;i++){
let category = this.categoriesfordisplay.women_for_display[i].replace(/"/g,"");
this.CatlogService(this.catalogselected,category,'women',this.ismainpage)
}
}
},
},
created(){
this.GetItemsToShowonMainPage()
}
}
</script>
<style>
</style>
How Do i trigger the GetItemsToShowonMainPage() function whenever the catalogselected varaible is changed.
It looks fine.
As #a-lau says, make sure the parent is updating the catalogselected prop
Btw, you can write your watcher this way and remove completely the created hook:
watch: {
catalogselected: {
handler: "GetItemsToShowonMainPage",
immediate: true
}
}
If you still have issues you might want to write a minimal reproduction on https://codesandbox.io/s/vue
In a standalone Vue.js script I can mix functions and Vue data:
var vm = new Vue ({
(...)
data: {
number: 0
}
(...)
})
function return100 () {
return 100
}
vm.number = return100()
I therefore have a Vue instance (vm) which data is directly addressable via vm.<a data variable>)
How does such an addressing works in a component, since no instance of Vue is explicitly instantiated?
// the component file
<template>
(...)
</template>
<script>
function return100 () {
return 100
}
export default {
data: function () {
return {
number: 0
}
}
}
// here I would like to set number in data to what return100()
// will return
??? = return100()
</script>
You can achieve the target by using code like this.
<template>
<div>{{ name }}</div>
</template>
<script>
const vm = {
data() {
return {
name: 'hello'
};
}
};
// here you can modify the vm object
(function() {
vm.data = function() {
return {
name: 'world'
};
}
})();
export { vm as default };
</script>
But I really don't suggest you to modify data in this way and I think it could be considered as an anti-pattern in Vuejs.
In almost all the use cases I met, things could be done by using Vue's lifecycle.
For example, I prefer to write code with the style showed below.
<template>
<div>{{ name }}</div>
</template>
<script>
export default {
data() {
return {
name: 'hello'
};
},
mounted() {
// name will be changed when this instance mounted into HTML element
const vm = this;
(function() {
vm.name = 'world';
})();
}
};
</script>