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Complete TEMPLATE for REACT SPA (2021)

Complete template for REACT SPA (2021)



This TEMPLATE allows you to derive a project in a fast and clean way.
You have full control of the code as it is a classic CRA.
Many typical management problems are solved in the template
and it can be a good way to learn.

git clone
cd jon-template
install npm modules:
npm install
install MSW
npx msw init public/ --save
npm run start

The template is based on a library for managing the STORE in REACT:
and the concepts solved are:


When you use REACT for medium-large projects the first urgency is:

Separate the VIEW from the BUSINESS LOGIC
There are libraries for this! The most famous is REDUX
But, in my opinion, it is too long-winded and cumbersome.
So I started using the native REACT methods REDUCER and PROVIDERS
Eventually I ended up with a VERY VERY light bookcase inspired by VUEX!
Check it out!


There isn't much to say! If you want to make an app in REACT it is better to use CRA
You just don't have to manage babel andwebpack:
The APP will have a pre-established and reproducible setup.


The structure in the file system of the TEMPLATE:


it contains everything that is not a PAGE or DIALOG.
In general: conceptually "reusable" components.


Specific hooks used in the APP.


The translation json for i18n


  • ajax/handlers the functions for mock responses to HTTP requests
  • data the mock data to be used instead of the DB


REACT components that rendering the "body" of the layout.
You intuitively start from the page, which is unique,
then go to the component that (theoretically) is used in several places.


They are services accessible at any point in the program. They allow you to access an external service, translate, make calculations etc etc


They are the CONTROLLERs of the VIEWs.
The STORE is not the perfect solution but it works well in most cases!

BUSINESS LOGIC simply has to modify or read the STORE
without worrying about how VIEW is implemented.

It is ESSENTIAL for large projects because it allows you to:

  • distribute the code on several units, improving maintainability
  • clearly separates the VIEW from the BUSINESS LOGIC
  • you can modify the VIEW or the CONTROLLER (keeping the same BINDs) independently

Maintaining the APP after years or by several people is something to be expected.
Impossible if you have a tree of components that pass functions and properties to you making them highly context dependent.

Using the STOREs I can copy and paste a component to another point of the APP without problems.
The components NOT HAVE PROPS (with the exception, of course, of "children" or "className").

Models and API

In reality in this TEMPLATE the APIs and the STOREs are "mixed"!
A questionable solution but given the simplicity of the API I didn't want to complicate the structure.
One could think of a "Models" folder for managing POCO objects
and "API" for HTTP requests.


Being a SPA, all data arrives via AJAX.
I built a very simple class here.
I wanted a default SINGLETON SERVICE that could keep some properties (for example baseUrl)
But if necessary, since it is a class, several instances can be created.

I can use STORE even outside REACT (and therefore in SERVICE AJAX)

For example, here I set the STATE busy of the STORElayout when the SERVICE is busy:
in SERVICE (outside REACT)

// I download the "layout" store
const { setBusy } = getStoreLayout()
// if necessary set "busy" == true
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While in the STORE layout

// I define the `busy` prop in readable / writable
export default {
    state: {
        busy: false,
    mutators: {
        setBusy: (state, busy) => ({ busy }),
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I can catch this event

function Header() {
    const { state: layout } = useLayout()
    return (
                // In this case the "progress" is displayed if the SERVICE AYAX is busy
                layout.busy && <LinearProgress />
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Sooner or later you will have to use it .... so better think about it first!
It's not just for "translating" the app
It allows you not to have the content directly in the VIEW ... which is more beautiful !!!
It is useful for testing in Cypress: you can use the translation PATH to locate components
instead of the text (which may change).

use the HOOK to import the t translation function

import { useTranslation } from 'react-i18next'
const {t} = useTranslation()
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Translate via PATH

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Or, outside of a COMPONENT, use the PLUGIN i18n

import i18n from "i18next"
const title = i18n.t("pag.default.dlg.router_confirm.title")
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The translations are inside JSON files in the src\locales directory



The APP must work offline! Of course with mock data

This allows to divide the tasks of those who do the FE and those who do the BE:
It is enough to share good documentation on the API (which must be done anyway)
You don't need the whole environment to develop.
It is also immediately "testable" (for example by Cypress).
Finally, the APP in mock can be presented as a demo to the CUSTOMER without "unexpected behavior" (= "panic")
Too many benefits!

I have configured and started MSW in /plugins/msw.js
It is called here starting a Service Worker

A Service Worker acts as a proxy between the APP and the WEB: "simulating" low-level network.
This is cool because it is completely transparent to the APP:
basically when you use fetch it still works ... even offline! The data is given to you by the Service Worker

In mocks/ajax/handlers there are simulated "CONTROLLERs"
In mocks/data there are ... the data! Used to emulate the DB

The APP starts the Service Worker if it is indevelopment or the REACT_APP_MOCK environment variable is" true "(string!)

Environment variables in CRA are documented here
However CRA (at compile time) takes from .env all variables that starting with REACT_APP
and makes them available in the browser

Example: To "simulate" the response to the request of a doc object by its id

HTTP request:
GET /api/docs/33

taken from: src/mocks/ajax/handlers/docs.js

import { rest } from "msw"
import list from "../../data/docs"

rest.get ('/api/docs/:id', (req, res, ctx) => {

    const id =

    const doc = list.find(item => == id)
    if (!doc) return res(ctx.status(404))

    return res(
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Also in this case it is easy to choose: reactrouter

CONDITIONAL RENDER based on the current browser URL?

Use Switch by specifying one or more paths

/* ATTENTION: the order is important */
    <Route path={["/docs/:id"]}>
        <DocDetail />
    <Route path={["/docs"]}>
        <DocList />
    <Route path={["/", "/users"]}>
        <UserList />
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Use the useHistory HOOK:

import { useHistory } from "react-router-dom";

export default function Avatar() {
    const history = useHistory()
    const handleClickProfile = e => history.push("/profile")
    return ...
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Use the browser's native history

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Use the useParams HOOK.

import { useParams } from "react-router"

export default function DocDetail() {
    const { id } = useParams()

    useEffect(() => {
        if (!id) fetchById(id)
    }, [id])

    return ...
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An example can also be found on the react-router-dom website here, I report it for completeness.

I created a custom hook useConfirmationRouter

that simply blocks navigation and asks for confirmation to continue.

I use it in the detail of the DOC here

Being the TEMPLATE a SPA:

  • On URL change it does not make any HTTP requests to the server but simply updates the rendering
  • Of course, the data is always retrieved via AJAX requests
  • The only requests "about the APP structure" is the first loading or reload of the page.
  • The SERVER must be set appropriately to always reply with the same page

Are you like me? Is installing a plugin always a doubt? What if this library doesn't do what I need? What if it becomes obsolete the day after putting it into production? What if the author vows to God never to touch a pc again? What if I notice that there is an unsolvable BUG in the library? And then ... do you want to have full control of the software ??
So ... this plugin could be replaced by managing the url with the STORE.
But I will not cover the subject here :D


It is very very simple! If we have to create a portal with many pages
Even if we render only one page at a time

with the classic import we load ALL COMPONENTs! Even the ones the user will never see!
To load COMPONENTs only if necessary you need to use a native REACT function: React.lazy

I do it in the Main here

const DocDetail = lazy(() => import('../../pages/doc/DocDetail'))

export default function Main() {
    return (
            <Route path={["/docs/:id"]}>
                <Suspense fallback={<div>LOADING...</div>}>
                    <DocDetail />
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Suspense is also a native REACT component.
Allows you to view an alternate render while the component is loading.


Of course you can make your own components (it doesn't take much)
but Material-UI is very used and solid!
Nothing else is needed!


First thing: link the STORE to the VIEW.
Remember useState BUT, instead of being in the COMPONENT REACT, it's in the STORE.

We define a STORE with a value in read / write

export default {
    state: {
        value: "init value",
    mutators: {
        setValue: (state, value) => ({ value }),
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I import the STORE and "binding" of its value in the COMPONENT REACT

import { useStore } from "@priolo/jon"

export default function Form() {

  const { state, setValue, getUppercase } = useStore("myStore")

  return <TextField 
        onChange={e => setValue(}
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A sandbox (that does NOT use MATERIAL-UI)
To find out more, check out Jon

However, in this TEMPLATE you can find the BINDINGS everywhere


Form validation is always left for last πŸ˜„
There is a simple mechanism for validating Material-UI components.

Just connect a value to a rule (with a HOOK)
and assign the obtained props to the MATERIAL-UI component

import { rules, useValidator } from "@priolo/jon";

function Form() {

    const { state: user, setSelectName } = useAccount()
    // I create a custom "rule". If there is a violation I return a string with the error
    const customRule = (value) => value?.length >= 3 ? null : "Enter at least 3 letters."
    // I link two "rules" with the STORE ACCOUNT property ""
    const nameProps = useValidator(, [rules.obligatory, customRule])
    // ... and I get "nameProps"

    return <TextField autoFocus fullWidth
        // report an error if the value does not meet one of the rules
        onChange={e => setSelectName(}
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And validate in the STORE before sending the data

import { validateAll } from "@priolo/jon"

const store = {
    state: {
        select: { name: "" },
    actions: {
        save: async (state, _, store) => {
            // check if there is an error in the displayed "rules"
            const errs = validateAll()
            // if there are errors I can view them ... or ignore them :)
            if ( errs.length > 0 ) return false
            // else ... save! 
    mutators: {
        setSelectName: (state, name) => ({ select: {, name} }),
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an example here


Once you understand how the STORES work, you use them for everything
... of course also to manage the THEME

In the STORE layout I put everything that characterizes the general appearance of the APP
but also the title on the AppBar, if the APP is waiting (loading ...), if the side DRAWERS are open, the main menu, the "message box", where the focus is set etc etc

However the THEME settings must be kept even when reload the page
The problem is that in this case the browser makes a new request to the server and the STORE is reloaded from scratch!
So I used the coockies to store the name of the selected THEME
you can see it here

The store theme is initially set with the cookie
and when the THEME is changed. (here)

export default {
    state: {
        theme: Cookies.get('theme'),
    mutators: {
        setTheme: (state, theme) => {
            Cookies.set("theme", theme)
            return { theme }
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Even if you use the cookies to memorize the name of the THEME
however, it is necessary to modify the STORE variable (more correctly "the STATE of the store")
Otherwise the VIEW does not receive the event!
In general the VIEW updates ONLY IF the state object of the STORE changes

Responsive Design

There are tools in MATERIAL-UI for this here
But what if we don't use MATERIAL-UI?

We can use the STORE! I initialize the STORE by hooking it to the window resize event

const store =  {
    state: {
        device: null,
    // chiamato UNA SOLA VOLTA per inizializzare lo store
    init: (store) => {
        const checkDevice = ()=> {
            const deviceName = window.innerWidth < 767 ? "mobile" 
                : window.innerWidth < 950 ? "pad"
                : "desktop"
        window.addEventListener("resize", (e) => checkDevice());
    mutators: {
        setDevice: ( state, device ) => ({ device }),
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And I use it to modify the VIEW based on the device

function MainDrawer () {
    const { state: layout } = useLayout()
    const variant = layout.device == "desktop" ? "persistent" : null

    return (
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Of course you can also use it for: classes and style css or conditional render



If I use a WEB APP and I copy the URL and send it to a friend

I expect him to see exactly what I see (with the same permissions of course)
Then the selected TABs, filters and sorting on the lists.

They must be kept in the search of the current URL (also called query string)
... in short, what is after the "?" in the URL

In STORE Route I can get or set a variable of query string which can be used in VIEW

An excerpt from the STORE:

export default {
    state: {
        queryUrl: "",
    getters: {
        getSearchUrl: (state, name, store) => {
            const searchParams = new URLSearchParams(
            return (searchParams.get(name) ?? "")
    mutators: {
        setSearchUrl: (state, { name, value }) => {
            const queryParams = new URLSearchParams(
            if (value && value.toString().length > 0) {
                queryParams.set(name, value)
            } else {
            window.history.replaceState(null, null, "?" + queryParams.toString())
            return { queryUrl: queryParams.toString() }
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then I use it in the list to filter the elements

function DocList() {
    const { state: route, getSearchUrl } = useRoute()
    const { state: doc } = useDoc()

    // it is executed only if the filter or the "docs" changes
    const docs = useMemo (
        // actually I do this in the STORE DOC
        () => {
            // I get the "search" value in the current url 
            let txt = getSearchUrl("search").trim().toLowerCase()
            // I filter all the "docs" and return them
            return doc.all.filter(doc => !txt || doc.title.toLowerCase().indexOf(txt) != -1)
        [doc.all, route.queryUrl]

    // render of docs
    return { => (
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meanwhile in the HEADER I have the text-box to modify the filter

import { useRoute } from "../../stores/route"

function Header() {
    const { getSearchUrl, setSearchUrl } = useRoute()
    return (
            onChange={value => setSearchUrl({ name: "search", value })}
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To recap: With the SearchBox I change the url
linked (via the store STORE route) to the VIEWDocList

and then this updates the list.
If I were to duplicate the page in the browser the filter would remain intact.


The AUTH is not complete (a matter of time ... I'll finish it)!

It is managed by the STORE auth here

JWT (JSON Web Token)

How does it work?

This is a token (ie an "identifier string") that the server gives to the client when the client logs in successfully.

At this point the client at each subsequent request no longer has to authenticate,
but it just puts the token in the HEADER of the HTTPS request.

Or the server puts the token in an HttpOnly COOKIE, and will find it on every request.
In this case javascript will not be able to access the token (more secure)

The server seeing the correct token and assumes that that HTTP request was made by someone who has already passed authentication.

User data is directly in the token (including permissions): there is no need to query the db
The token have an "expiration" forcing the client to re-authenticate to generate a new token.
Of course you have to use an HTTPS connection to be safe.

Assuming you want to implement the token in the HEADER:
The ajax plugin includes the token if available here

import { getStoreAuth } from "../stores/auth"

export class AjaxService {
    async send(url, method, data) {
        const { state:auth } = getStoreAuth()

        const response = await fetch(
                method: method,
                headers: {
                    "Content-Type": "application/json",
                    ...auth.token && { "Authorization": auth.token }
                body: data,

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The token is accessible in the STORE auth.
I used cookies to avoid having to login again on "reload" (it does not work with MSW)

Cookies should only be used with HTTPS

import Cookies from 'js-cookie'

export default {
    state: {
        token: Cookies.get('token'),
    getters: {
        isLogged: state => state.token != null,
    mutators: {
        setToken: (state, token, store) => {
            if (token == null) {
            } else {
                Cookies.set('token', token)
            return { token }
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Template di uno stack tecnologico
per realizzare un Front End SPA

















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