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How to share data between components in angular

I use observable to send a value from one component to another (data is sent to the subscriber after clicking on this other component, i.e. via subject) I subscribe in another component and everything works fine until I refresh the page, after refreshing the page the component is recreated and after recreation the subscriber has no data as he did not go through the first component.How can I solve the problem?
I tried using rxjs operators as shareReplay but it didn't work like shareReplay

As your Angular app is destroyed and rebuilt when the page is refreshed, unfortunately you will lose all user state that is not saved somewhere. This is a common problem in building UIs so there are a number of tools available to combat this
Strategy:
Store your user state when an important change is made. This is called persisting state
Fetch and reapply your saved state on reload. This is called hydrating state
Options:
Persist to local storage and check for local storage values on reload to hydrate with
Persist within the users URL (simple values only), e.g. modifying the URL in some way which can be checked on reload. Assuming you are dealing with a single page, query parameters or fragments may be the way to go
Persist to a database via a POST/PATCH call and perform a GET request on reload to check for values to hydrate with
None of these methods are inbuilt into an RxJS operator (as far as I know) but we can easily leverage RxJS to achieve any of the above strategies with little effort. The tap operator is often used specifically to handle side effects, i.e. operations which should happen as a coincidence of an RxJS emission. That is precisely what we want here, in simple terms:
"If the subject emits a value, also trigger an operation which
persists the user state"
"On page load, check for any available saved user state and emit via the
relevant subject, hydrating the observables which the components will consume"
See example implementation below
tab.service.ts
type TabType = 'first' | 'second'
#Injectable({
providedIn: 'root'
})
export class TabService {
tabSelectedSubject: BehaviorSubject<TabType> = new BehaviorSubject<TabType>('first')
tabSelected$: Observable<TabType> =
this.tabSelectedSubject
.pipe(
tap(tab: TabType) => {
// ... your persist code here
this.saveTab()
},
distinctUntilChanged()
)
constructor() {
// ... your hydrate code here
this.fetchAndApplyTab();
}
saveTab(): void {
localStorage.setItem('tab', tab)
}
fetchAndApplyTab(): void {
const savedTab: TabType | null = localStorage.getItem('tab');
if (savedTab) {
this.tabSelectedSubject.next(savedTab)
}
}
}
In this case, we are exploiting the fact that our service is:
A singleton, so only loaded once per app (i.e. provided in the app root)
The service will be instantiated in the first component that loads which also injects it
This allows us to put our fetchAndApplyTab() logic in tab.service.ts's constructor and keep the code self-contained. However, depending on your use case, you may instead want to run fetchAndApplyTab() from your component manually itself.

This is happening because everything is in memory, and on page refresh all is lost, due the fact that angular app is re-initializing. You need to persist the state, for example write it into local storage, for this you could use "tap" operator from rxjs. And also in loading you could read data from localstorage end emit-it, for this you could use app_initializer hook.

there are 2 days majority to pass data between components
If both components are interconnected it means the parent or child
relationships then you can pass data with input-output decorators.
you can use the common service to share data between 2 components.
In SPA application if you refresh the browser then all in memory objects and observables are not present you need to again go back to the screen where it will be initialize.

Reload component data based on vuex state

I am creating one single admin panel for several web shops. To keep track of what website I am currently editing I have a website object in my vuex state. The website can be changed by a button that dispatches an action on the state.
The admin dashboard page is a page showing statistics for the selected website, the data for these statistics is currently saved on the page component itself.
Now I have a problem when I change to another website when I am on the dashboard. Because the url is the same for the dashboards, the statistics don't change. I suppose this is because vue-router has not detected a change to the url so there is no need to reload the component, however I would like this to happen when the website is changed. Or at least a way to know that the website has changed so I could manually call the ajax source again.
I have just started using vue a few weeks ago and did not find a way to accomplish this.

You can subscribe to Vuex mutations and actions: https://vuex.vuejs.org/api/#subscribe
On the created hook of your admin dashboard component, assuming you're injecting the Vuex store, you could have something like:
created: function() {
this.unsubscribe = this.$store.subscribe((action, state) => {
if (action.type === 'changeWebsite') { // Whatever your action is called
this.updateWebsiteData(action.payload); // Method to update component data
}
});
},
beforeDestroy: function() {
this.unsubscribe();
},

React+Javascript:-Component will update is getting called too many times causing my application to crash

componentWillUpdate() {
//Axios GET method for getting all the trades
//Adding data of db into mobx store/or syncing data of db and store
axios.get(`http://localhost:8091/trade`)
.then(res => {
this.props.store.arr = res.data;
})
}
This piece of code causing my browser to crash, my laptop to not responding.
Actually, whenever i was trying to delete the row of table containing trade by click of button then the trade was deleted but it took the need of refresh to see that the trade is deleted.
This was because my mobx store and db were not in sync.So as soon i refresh the (REST api) controller updates data in my mobx store.After this i can see that trade is deleted.
So in order to remove the need of refresh i thought to use component will update method.Within that method i tried to sync mobx store with controller data (db data).It worked but it caused the browser to take more than 2.5 gb of memory & at this point all the running applications starts getting crashed also.
So what is the good way to achieve the desired result?
Note i don't know why component will update is getting called too many times.
But i can verify the it because i can see the selection statements(of database) in spring (my server which is sending data to controller ).
Putting the above code inside component did mount is not removing the need of refresh but it is not causing the browser to crash also.

You should not be doing this type of operation in this lifecycle hook. You should use componentDidMount instead for any remote calls that need to happen. However since you are using mobx, you really should not be having these problems as they handle these type of problems for you with the observer pattern. Please read: https://mobx.js.org/getting-started.html to get up to speed and you should have no issues at that point.

Something in your component's props or state is causing it to update often, which is causing a lot of calls to the api. Your best bet would be to find out what is causing those updates and use nextState and nextProps arguments supplied to componentWillUpdate to check and send an api call only when needed. Something like:
componentWillUpdate(nextProps,nextState) {
if (nextProps.needToGetApi !== this.props.needToGetApi) {
//Axios GET here, so that unrelated prop/state change does not cause this to run
}
}
Hint: Add a breakpoint in componentWillUpdate and see what props or state mutations are happening on each call.

Should I use redux dispatch during initial rendering?

I'm trying to build a E-Commerce Store and it requires that I initially load a list of trending products on the home page.
Here, I can simply do without redux and simply display the data (roughly) of this sort
const trendingProducts = await get('/api/trendingProducts')
render(){
<TrendingProducts data={this.trendingProducts.data} />
}
I am using redux in my application. So should I do a dispatch elsewhere to fetch the trending products ?
All in all, Should I always handle every single fetch / render using only Redux dispatch ?

Redux is a store management for your application's state. Redux's dispatch is used to dispatching actions that aims to update your application's state in some way.
Hence if your application logic requires displaying information that belongs to your application's state - you need to take it from Redux store. If such information is not yet available into Redux store - you need to obtain it from some source (e.g. fetch) and use dispatch to update your application's state. If information, you're trying to display is not part of your application's state - you can display it directly, but in this case you'll need to handle React lifecycle events by yourself too since React re-draws components upon component's state change.
UPDATE: Your example code will work fine if you'll put your trendingProducts into component's state:
class MyComponent {
constructor() {
super();
this.state = {
trendingProducts: {}
}
}
componentWillMount() {
fetch('/api/trendingProducts').then(data => this.setState({trendingProducts: data}));
}
render() {
return (
<TrendingProducts data={this.state.trendingProducts}/>
)
}
}

That is very subjective and there is no correct answer but I can tell you by my experience.
Always keep your business logic separate from your component
If you're making API calls then you should definitely dispatch an action rather writing this in your component because there are lot of redux-like stores are emerging and it might happen that later you want to change your store using some different architecture. Your view layer should be independent on your API calls (business logic). In this way, while refactoring your app again, you'll just have to change the logic and your view will remain the same.
I'm writing this on my experience where we started refactoring the whole app from backbone to React. We had models and collections, we changed the whole html but we didn't change any business logic initially, just the views were deprecated but later we removed the business logic too using redux (iteratively). You should write your code in such a way that it has maximum reusability after all that's what React is and that's how you should write your front-end code.
Also, the component's state can reside in component where the whole app doesn't get affected. e.g. showing or hiding of a third-pane or overlay etc.

Accessing Store within Redux and React Native app

I'm starting to develop an app that will be making calls to an API that will require the inclusion of a JWT that I plan on storing within the Redux store.
Typically you can access the Redux store by mapping a particular part of the store to a component's state with mapStateToProps() and connect(), however I'd like to access the Redux store within a file that will not end up being a React component/container - just a pure js file that will be handling the API calls.
Is this possible?

You can use the getState() function of the store returned by createStore. You can use this inside a function that fishes the needed data from the state.
const myImportantData = () => store.getState().my.deep.data;
The version above uses the store directly, as in a global variable. This prevents you from using more than one store in your process. Normally this is what you want, but this isn't true when running on the server. That said, on the server you'll likely not need the JWT access anyway.
If you do need to swap stores, however, then you can pass it as a parameter or close over a store local variable:
const getDataGrabber = store => () => store.getState().my.deep.data;

Yes, it is possible.
Redux is framework agnostic, although it was made with React in mind.
The mapStateToProps() and connect() methods aren't part of the core Redux library but of the helper library 'React-Redux' which provide bindings specifically for Redux use within React.
It's worth checking out Dan Abramov's Getting started with Redux series to get the principle of how the guts of Redux works.
An example of which are Video 6 and Video 7 where he discusses the Redux store and describes the three methods that make it up:
store.getState // gets the current application state
store.dispatch // changes the current application state by dispatching an action
store.subscribe // suscribes to changes and re-renders the app using the
// current state
The videos go into a fair bit of detail as to how to register the reducers with the store, so the series should prove very helpful.