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How to send data to component in vue js?

How do I send data to a component in Vue.js? I got a response from the server on the button click event, and now I want to send this response to the component and display on list using v-for.
Here is my code:
var store = new Vuex.Store({
state: {
Item: []
},
mutations: {
getItems: function (state) {
}
},
actions: {
fetchData:function (context) {
Vue.http.get('data.json').then(function(response){
alert('dd')
}, function(error){
console.log(error.statusText);
});
}
}
})
var httprequest = Vue.extend({
"template": '#http_template',
data: function () {
return {
items: store.state.Item
}
},
methods: {
fetchData: function () {
store.dispatch('fetchData')
},
}
})
Vue.component('httprequest', httprequest);
var app = new Vue({
el: '#App',
data: {},
});

You have almost done everything correct. Only thing you are missing is after getting data, you are not assigning it to state.Item. Please check the below code:
var store = new Vuex.Store({
state: {
Item: []
},
mutations: {
getItems: function(state, items) {
items.forEach(function(item) {
state.Item.push(item)
})
}
},
actions: {
fetchData: function(context) {
Vue.http.get('data.json').then(function(response) {
context.commit('getItems', response.data)
}, function(error) {
console.log(error.statusText);
});
}
}
})
working example can be found here.

You don't send data to components. You set up reactive pipes and the data moves around when it needs to. In your case, with vuex, you want to register store.state.items on the data of your component.
You can use a prop if you want, but you still need to do the registration in the parent's data. If your component is a singleton, intended for this page only, you're better registering what you need directly in the data of the component.

In general vue follows the principle that data goes the DOM tree down via properties and up via events. See for example https://v2.vuejs.org/v2/guide/index.html#Composing-with-Components.
Thus to get data into your component define a property myProp inside your component and when using your component bind it via v-bind:myProp="myData".
To get data back from your component use this.$emit('myUpdateEvent', myUpdatedData) and listen to the event by using v-on:myUpdateEvent="myUpdateHandler".

Parent's data change does not update child component in vuejs

I have the following:
Vue.component('times-updated', {
template: '<span>Times Updated: {{ timesUpdated }}</span>',
data: function() {
return {
timesUpdated: this.$parent.myData.timesUpdated
}
}
});
var vm = new Vue({
el: '#test',
data: function() {
return {
myData: {}
}
}
})
setInterval(function(){
$.ajax({
url: `${window.location.href}/json`, // This just returns an array : array.timesUpdated: 2 etc
}).done(function (data) {
vm.myData = data; // changes this data
});
}, 1000)
and am using the following html:
<div class="test">
<times-updated></times-updated>
</div>
I poll a REST API that returns an array which includes a timesUpdated property:
{
timesUpdated: 5
}
My intention is that every second I use jQuery's $.ajax method to call the API, update the myData data object on vm, which would then update the times-updated component.
The code works on initial page load, the times-updated component can retrieve the value on its parent's myData property, but whilst I have confirms that vm.myData does reflect the new value from the API, the component doesn't update its display to show the new count.
What am i doing wrong?

The data function is only called once during the life cycle of the component; when it is initially created. So essentially your component is just displaying the value as it existed when the component was created.
Additionally, it's generally bad practice to reach out of a component to get a data value. Vue is props down, events up. You should convert your component to use a property.
Vue.component('times-updated', {
props:["times"],
template: '<span>Times Updated: {{ times }}</span>',
})
The fact that you are using a function to define the Vue in this particular case doesn't really matter, it's just not a typical practice. Components require a function because they need an isolated scope.
Here is an example.

That callback is required only in components
// vue instance
new Vue({
data: {
status: true
}
};
// vue components (callback)
Vue.component('custom-component', {
data: function() {
return {
status: false
}
}
});

How to get the latest data from parent to child components after page refresh

I am working on a project and using Vue.js for the frontend. I have following code in the main.js file.
new Vue({ // eslint-disable-line no-new
//el: '#app',
router,
data () {
return {
friends: []
}
},
methods: {
getFriends: function () {
return this.friends;
}
},
created: function () {
this.$http.get('/user/' + this.getUserIDCookie('userID') +
'/friends').then(function (response) {
this.friends = response.data;
});
},
components: {
'nav-bar': require('./components/Navigation.vue')
},
template: `
<div id="app">
<nav-bar></nav-bar>
<router-view class="router-view"></router-view>
</div>`
}).$mount('#app');
In one of the pages(for ex. when the page is redirected to localhost/#/user/1/details, I am retrieving the friends' list from main.js like below:
<script type="text/babel">
export default {
name: 'profile',
data: function () {
return {
user: {},
friends: []
}
},
methods: {
// Some methods
},
created: function () {
this.friends = this.$root.getFriends();
}
}
</script>
The problem arises when I refresh the current page. After page refresh, this.friends is null/undefined because this.$root.getFriends() is returning null/undefined. I can move it to user component, but I want to keep it in main.js so that GET call is used once and data will be available to the whole application.
Any input regarding how to solve this issue would be great. I am using Vue 2.0.1

Really, what you want to do, is pass the data the component needs as props.
The dirt simple easiest way to do it is this.
<router-view class="router-view" :friends="friends"></router-view>
And in your profile component,
export default {
props:["friends"],
name: 'profile',
data: function () {
return {
user: {},
friends: []
}
},
methods: {
// Some methods
}
}
If you want to get more sophisticated, the later versions of VueRouter allow you to pass properties to routes in several ways.
Finally, there's always Vuex or some other state management tool if your application gets complex enough.

The problem is that when you refresh the page, the whole app reloads, which includes the get, which is asynchronous. The router figures out that it needs to render details, so that component loads, and calls getFriends, but the asynchronous get hasn't finished.
You could work around this by saving and pulling the Promise from the get, but Bert's answer is correct: the Vue Way is to send data as props, not to have children pull it from parents.

vuejs v2.0 pass data to component

I built an app on Laravel 5.3 using vue.js and im starting to move over to vue.js to make the pages dynamic. I got everything working on a single page so want to convert that over to a component but after doing so I get the following error:
[Vue warn]: Error when rendering component <homepage> at C:\xampp\htdocs\.......
TypeError: Cannot read property 'nxt_weekly' of undefined
I was passing data to the view like so:
const app = new Vue({
el: '#app',
mounted: function () {
this.fetchEvents();
},
data: {
loading: true,
stats: []
},
methods: {
fetchEvents: function () {
this.$http.get('home/data').then(function (response) {
this.stats = response.body;
this.loading = false;
}, function (error) {
console.log(error);
});
}
});
In stats[] is where I hold the JSON response from the API and then call them all in my view like so:
<span class="stat" v-text="'stats.nxt_today'"></span>
....
....
This works but when I switch over to creating a component the errors listed above show, my new code is:
Vue.component('homepage', require('./components/Homepage.vue'),{
mounted: function () {
this.fetchEvents();
},
data: function () {
return{
loading: true,
stats: []
}
},
methods: {
fetchEvents: function () {
console.log('running here');
this.$http.get('home/data').then(function (response) {
this.stats = response.body;
this.loading = false;
}, function (error) {
console.log(error);
});
}
}
});
What am I doing wrong? How come my stats[] object is now empty when the component is trying to access it?

You need to pass your stats as a property to the component using v-bind, as shown below:
<homepage v-bind:stats="stats"></homepage>
The above needs to be done in your root template. And in your homepage component, you can receive the value in props as follows:
Vue.component('homepage', {
props: ["stats"],
mounted: function () {
// ...
},
// ...
}
Within the template of this component, you will be able to access stats.nxt_today normally.
By the way, is your stats an array or an object? You have defined it as an empty array initially, but accessing it as an object.
If you still have issues, you can use vue-devtools to view all the objects available within a component.

How to call a vue.js function on page load

I have a function that helps filter data. I am using v-on:change when a user changes the selection but I also need the function to be called even before the user selects the data. I have done the same with AngularJS previously using ng-init but I understand that there is no such a directive in vue.js
This is my function:
getUnits: function () {
var input = {block: this.block, floor: this.floor, unit_type: this.unit_type, status: this.status};
this.$http.post('/admin/units', input).then(function (response) {
console.log(response.data);
this.units = response.data;
}, function (response) {
console.log(response)
});
}
In the blade file I use blade forms to perform the filters:
<div class="large-2 columns">
{!! Form::select('floor', $floors,null, ['class'=>'form-control', 'placeholder'=>'All Floors', 'v-model'=>'floor', 'v-on:change'=>'getUnits()' ]) !!}
</div>
<div class="large-3 columns">
{!! Form::select('unit_type', $unit_types,null, ['class'=>'form-control', 'placeholder'=>'All Unit Types', 'v-model'=>'unit_type', 'v-on:change'=>'getUnits()' ]) !!}
</div>
This works fine when I select a specific item. Then if I click on all lets say all floors, it works. What I need is when the page is loaded, it calls the getUnits method which will perform the $http.post with empty input. In the backend I have handled the request in a way that if the input is empty it will give all the data.
How can I do this in vuejs2?
My Code: http://jsfiddle.net/q83bnLrx

You can call this function in the beforeMount section of a Vue component: like following:
// .....
methods: {
getUnits: function() { /* ... */ }
},
beforeMount() {
this.getUnits()
},
// ......
Working fiddle: https://jsfiddle.net/q83bnLrx/1/
There are different lifecycle hooks Vue provide:
I have listed few are :
beforeCreate: Called synchronously after the instance has just been initialized, before data observation and event/watcher setup.
created: Called synchronously after the instance is created. At this stage, the instance has finished processing the options which means the following have been set up: data observation, computed properties, methods, watch/event callbacks. However, the mounting phase has not been started, and the $el property will not be available yet.
beforeMount: Called right before the mounting begins: the render function is about to be called for the first time.
mounted: Called after the instance has just been mounted where el is replaced by the newly created vm.$el.
beforeUpdate: Called when the data changes, before the virtual DOM is re-rendered and patched.
updated: Called after a data change causes the virtual DOM to be re-rendered and patched.
You can have a look at complete list here.
You can choose which hook is most suitable to you and hook it to call you function like the sample code provided above.

You need to do something like this (If you want to call the method on page load):
new Vue({
// ...
methods:{
getUnits: function() {...}
},
created: function(){
this.getUnits()
}
});

you can also do this using mounted
https://v2.vuejs.org/v2/guide/migration.html#ready-replaced
....
methods:{
getUnits: function() {...}
},
mounted: function(){
this.$nextTick(this.getUnits)
}
....

Beware that when the mounted event is fired on a component, not all Vue components are replaced yet, so the DOM may not be final yet.
To really simulate the DOM onload event, i.e. to fire after the DOM is ready but before the page is drawn, use vm.$nextTick from inside mounted:
mounted: function () {
this.$nextTick(function () {
// Will be executed when the DOM is ready
})
}

If you get data in array you can do like below. It's worked for me
<template>
{{ id }}
</template>
<script>
import axios from "axios";
export default {
name: 'HelloWorld',
data () {
return {
id: "",
}
},
mounted() {
axios({ method: "GET", "url": "https://localhost:42/api/getdata" }).then(result => {
console.log(result.data[0].LoginId);
this.id = result.data[0].LoginId;
}, error => {
console.error(error);
});
},
</script>

methods: {
methodName() {
fetch("url").then(async(response) => {
if (response.status === 200) {
const data = await response.json();
this.xy = data.data;
console.log("Success load");
}
})
}
}

you can do it using created() method. it will fire once page fully loaded.
created:function(){
this.fillEditForm();
},