I have inherited a Node/Express code base and my task is to implement a notification alert in the navigation menu. The app database has a table of 'pending accounts', and the alert needs to expose the number of these pending accounts. When an account is 'approved' or 'denied', this notification alert needs to update and reflect the new total of pending accounts.
I know how to do the styling and html here, my question is how best to instantiate, maintain and pass a global dynamic variable that reflects the number of pending accounts, and how to get this variable exposed in the header view which contains the navbar where the notification is to be displayed.
This project a pretty standard Node/Express app, however it uses the view engine Pug. At the root of the view hierarchy is a layout.pug file, which loads most of the scripts and stylesheets, and this layout view in turn loads the header Pug view. When this header view loads, and every time it loads, I need this updated 'pending accounts count' value available to insert into the header view. This is what I am at a bit of a loss on how to go about.
Below is the layout.pug markup with the inclusion of the header pug view. Everything else in the project is pretty straightforward vanilla Node/Express I believe, but I am not very experienced with this stack so if any other code is needed please don't hesitate to ask and I will post. Thanks.
doctype html
html(lang="en")
head
meta(charset='utf-8')
meta(http-equiv='X-UA-Compatible', content='IE=edge')
meta(name='viewport', content='width=device-width, initial-scale=1.0, shrink-to-fit=no')
meta(name='theme-color', content='#4DA5F4')
meta(name='csrf-token', content=_csrf)
script(src="https://cdn.jsdelivr.net/npm/axios/dist/axios.min.js")
block head
body
include partials/header
I tried including a script in my header.pug view, which contains the navbar element that I want to append the notification too...
link(href='/css/header/header.css' rel='stylesheet')
script(src='/js/registration/registrationsTable.js')
...
Which would run the following function on DOM load....
function getNumberOfPendingRegistrations() {
axios({
method: 'get',
url: '/admin/getNumberOfPendingRegistrations'
}).then((response) => {
if (response.status === 200) {
const { numPendingUsers } = response.data;
console.log(response.data);
} else {
console.log(response.status);
}
})
.catch((error) => {
console.error(error);
});
}
(() => {
document.addEventListener('DOMContentLoaded', () => {
getNumberOfPendingRegistrations();
which would then call the following express function....
exports.getNumberOfPendingRegistrations = (req, res) => {
RegisteredUser.find({ status: 'PENDING' }, (err, allPendingUsers) => {
if (!err) {
let numPendingUsers = 0;
allPendingUsers.forEach(() => {
numPendingUsers++;
});
return res.send(200, { numPendingUsers });
}
console.log('error');
throw err;
});
};
which would then return numPendingUsers to the axios then() function and make that variable available to the header.pug view here....
li.nav-item
a.nav-link(href='/admin/registeredUsers')
span.fa-solid.fa-pen-to-square(style="font-size: 0.7em;")
span(style="margin-left: 0.1em;") Registrations
span.notification=numPendingUsers
NumPendingUsers returns correctly to the axios .then() promise, but is somehow never made available in the header.pug view. It is always undefined. I'm not sure if its a timing issue w when the DOM is loaded, or if I'm making the variable available in .then() incorrecly or what. And also I feel like there must be a simpler way to accomplish all of this.
Figured out that I simply needed to implement a middleware to pass this data to every route. Duh.
Related
when i am using list.save() method a object other than customList name which is favicon.ico is also
saving as record in following cod, Why am i gatting favicon.ico as object.
app.get('/:listRoute',function (req,res) {
const customList=(req.params.listRoute);
List.findOne({name:customList }, function (err,result) {
if (!err) {
if (!result) {
const list=new List({
name: customList,
items: defaultItems
})
list.save();
} else {
console.log(result);
res.render('list', {
listTitle: result.name,
latestItems: result.items})
}
}
});
})
When you visit a website (any URL on that website), a browser will typically also send a request to that same domain for /favicon.ico so see if the web site offers an icon to be a visual representation of the site.
Since you are using a wildcarded top level route:
app.get('/:listRoute', ...)
That will get hit by the request for /favicon.ico. Some other urls you also may need to watch out for being requested are: /robots.txt, /humans.txt, /sitemap.xml, /ads.txt.
There are a number of ways to work around this:
Your wildcard route can first check req.url or req.params.listRoute to see if it's something it should ignore.
You can place other top level routes that you want to keep out of your wildcard route in a position before this route so they don't end up in this one.
Don't use a top level wildcard route. Instead, use something like /list/:listRoute so it won't automatically match any top level http request. Your use of a top level wildcarded route interferes with other future uses of your site and can create backwards compatibility going forward when you want to add other top level routes to your site. Imagine if sometime in the future, you want to add /contact or /login or /logout. Those all conflict with /:listRoute.
Try to add a callback function to the list.save();
Let me know if this works. The reason is maybe because of sync issues. eg: time taken by mongoDB to update the first document & save > the time taken by the 'Get' method to redirect to itself. Therefore by adding this callback it kinda make sure the code gets saved first and err checked before the redirect.
eg:
list.save(function(err){
if(!err) {
console.log("list is successfully saved"); //log is optional
res.redirect("/" + listRoute);
}
});
When fetching route data using params with express,the entered data easily we can log.But if not adding top-level route and just trying to get the required route eg:
app.get("/:requireddata",function(req,res){
const data = req.params.requireddata;
});
in this case, when loading main page the favicon.ico will generate as a result.
So for getting an exact result, that's when only loading requireddata route we can get the result by using higher level route.
In case there is no higher-level route add just an additional route before requireddata as shown below:
app.get("/add/:requireddata",function(){});
Here /add/ is an additional route for avoiding favicon.ico
For me this worked, so if this information is useful just go head.
Hey there I also came across this exact issue.
So here is my solution to that.
Just enclose everything in a if block and there you go. DONE !!!!
app.get("/:name", function (req, res) {
if (req.params.name != "favicon.ico") {
const name = _.capitalize(req.params.name);
List.findOne({ name: name }, (err, foundList) => {
if (!err) {
//new list with default items created
if (!foundList) {
const list = new List({
name: name,
items: defaultItems,
});
list.save();
res.redirect("/" + name);
} else {
res.render("list", {
listTitle: foundList.name,
newListItem: foundList.items,
});
}
}
});
}
});
P.s.:- It will throw some error from mongo but that'll not affect the overall working.
Hope this helps.
Let's say I have a user's account information stored in localStorage (client side). I need my Next.JS app to render the webpage's navbar based on what's stored in localStorage (login or logout button). How can I first obtain the value from the client and then render the page? Or perhaps that isn't even what Next.JS is meant to do?
You can do something like this:
Use a variable in the state to prevent the page from being rendered
Use componentDidMount to load data from localStorage
When data is loaded, setState to allow component to be rendered.
It's a react issue, not a next.js issue.
You could use Conditional rendering for step 1.
Also read up on state here, and lastly componentDidMount.
Update:
Nowadays, I would opt for a React hooks implementation instead, but the idea still stands. useEffect can largely accomplish this with some nuances in some situations.
I also realize that there are some possible caveats with NextJS and SSR logic specifically, so this response may not be sufficient. In such cases, I would also look into some other responses below.
As mentioned at https://stackoverflow.com/a/54819843/895245 I haven't been able to truly get localStorage before the first render, only show a fallback page until that happens.
The fundamental issue is that Next.js maps one URL to one pre-render. And React hydration requires the initial server HTML to match the JavaScript structure:
React expects that the rendered content is identical between the server and the client. It can patch up differences in text content, but you should treat mismatches as bugs and fix them. In development mode, React warns about mismatches during hydration. There are no guarantees that attribute differences will be patched up in case of mismatches. This is important for performance reasons because in most apps, mismatches are rare, and so validating all markup would be prohibitively expensive.
That quote is not very clear if text-only changes work or not but the minimal test below shows that it raises a warning in that case, so you don't want to use it.
Therefore the only sure-fire way it to use useEffect to update the page afterwards.
However, when I've tested, the correct render with localStorage shows up so quickly that the intermediate one it is not noticeable at all, I'm not sure it even happens. The only problem is if you make different API calls on each case, see section "Differentiate between "not logged in" and "haven't decided yet" to avoid doing extra API calls" below for an example of that.
What I would like to do is to give a slightly more concrete idea about what was mentioned in that answer.
SWR example
Here is a complete runnable example where the navbar shows login status: https://github.com/cirosantilli/node-express-sequelize-nextjs-realworld-example-app That repository is a fork of this one, both of which are Next.js implementations of the awesome realworld project.
The fallback in that case is just the signed out view of the blog pages, which already contain the key information users are likely to want to see, and can be cached e.g. with ISR.
That demo uses SWR to make the code slightly simpler. The key parts are:
navbar code
login code
The key parts of the code there are:
navbar:
import useSWR from "swr";
const Navbar = () => {
const { data: currentUser } = useSWR("user", key => {
const value = localStorage.getItem(key);
return !!value ? JSON.parse(value) : undefined;
});
login:
import { mutate } from "swr";
const LoginForm = () => {
const handleSubmit = async (e) => {
// Get `user` data structure from API.
mutate("user", data?.user);
We see that when the user logins, we call mutate on the "user" global identifier.
This redraws all components that contain that hook, which includes the navbar, as it setup the hook with the useSWR call.
This way, login first redraws the navbar, and then redirects you to home, so that the home page will have the redrawn navbar immediately. Without mutate, only the page body would redraw, not the navbar.
With this setup:
if you put a console.log(currentUser) just below useSWR, you see that it gets called twice.
So what happens is that it first returns immediately with a cached value (undefined) and the first render starts.
It then starts an async call to the cache, and when that returns, the hook triggers a re-render of the component, and the print happens again with the current user value.
This only happens on initial hydration during refresh/first hit. During internal page changes, there is just a single render.
All of this happens so fast that I can't see the page draw without hte local storage at all, not even with the Chromium debugger timeline frame inspection.
if we add a 2 second delay to the localStorage getter however:
const { data: currentUser } = useSWR("user", async (key) => {
await new Promise(resolve => setTimeout(resolve, 2000))
const value = localStorage.getItem(key);
return !!value ? JSON.parse(value) : undefined;
});
we do observe an intermediate page state with the user logged out, so it could in theory happen.
How it would look like without SWR
Of course, we wouldn't need to use SWR to achieve this.
The SWR documentation gives us the rationale of how thing would look like without SWR https://swr.vercel.app/getting-started to motivate their library.
You would either need to move the state up to a common parent of the login form + navbar, or you could use Context.
function Page () {
const [user, setUser] = useState(null)
// fetch data
useEffect(() => {
const value = localStorage.getItem(key);
const user = !!value ? JSON.parse(value) : undefined;
setUser(user)
}, [])
// global loading state
if (!user) return <Spinner/>
return <div>
<Navbar user={user} />
<Content user={user} />
</div>
}
// child components
function Navbar ({ user }) {
return <div>
...
<Avatar user={user} />
</div>
}
function Content ({ user }) {
return <h1>Welcome back, {user.name}</h1>
}
function Avatar ({ user }) {
return <img src={user.avatar} alt={user.name} />
}
As mentioned at What is difference between lifecycle method and useEffect hook? useEffect is the hook analogue to componentDidMount.
Checking typeof localStorage === 'undefined' leads to a warning
React doesn't like that and warns with something like:
Expected server HTML to contain a matching"
as it notices the difference between hydrated and non-hydrated pages: React 16: Warning: Expected server HTML to contain a matching <div> in <body>
Tested on Next.js 10.2.2.
Minimal reproducible example
Just to play with and see exactly what happens:
pages/index.js
import Link from 'next/link'
import React from 'react'
export default function IndexPage() {
console.error('IndexPage');
let [n, setN] = React.useState(0)
if (typeof localStorage === 'undefined') {
n = '0'
} else {
n = parseInt(localStorage.getItem('n') || '0', 10)
}
return <>
<Link href="/notindex">notindex</Link>
<div
onClick={() => {
localStorage.setItem('n', n + 1)
setN(n + 1)
}}
>increment</div>
<div
onClick={() => {
localStorage.removeItem('n')
setN(0)
}}
>reset</div>
<div>{n}</div>
</>
}
pages/notindex.js
import Link from 'next/link'
export default function NotIndexPage() {
return <Link href="/">index</Link>
}
package.json
{
"name": "test",
"version": "1.0.0",
"scripts": {
"dev": "next",
"build": "next build",
"start": "next start"
},
"dependencies": {
"next": "12.0.7",
"react": "17.0.2",
"react-dom": "17.0.2"
}
}
Run:
npm install
npm run dev
Now, if you:
open /
increment
refresh the page
react gives a warning because it notices that the 0 text was changed to 1:
Warning: Text content did not match. Server: "0" Client: "1"
If we click the internal links however to notindex and back, we don't see the warning. This is because hydration is only done on the initial page refresh, further changes are done in Js only.
What we have to do instead is something like this:
import Link from 'next/link'
import React from 'react'
export default function IndexPage() {
console.error('IndexPage');
let [n, setN] = React.useState(0)
React.useEffect(() => {
console.error('useEffect');
setN(parseInt(localStorage.getItem('n') || '0', 10))
}, [])
return <>
<Link href="/notindex">notindex</Link>
<div
onClick={() => {
setN(n + 1)
localStorage.setItem('n', n + 1)
}}
>increment</div>
<div
onClick={() => {
localStorage.removeItem('n')
setN(0)
}}
>reset</div>
<div>{n}</div>
</>
}
Differentiate between "not logged in" and "haven't decided yet" to avoid doing extra API calls
OK, I had another issue: I was making unnecessary API calls, because first the page thought the user was logged out, and then it thought it was logged in, and each of those needed to do different API calls.
Unlike starting to render the wrong page, this would actually have server load consequences, so it was not acceptable.
The solution I used was to differentiate between:
undefined: haven't decided
null: not logged-in
and not make any requests on undefined.
Here's a non-minimized demo:
https://github.com/cirosantilli/node-express-sequelize-nextjs-realworld-example-app/blob/2bbce5199d3a7efa19a3a58426bea25a1cd37579/front/ArticleList.tsx#L33
https://github.com/cirosantilli/node-express-sequelize-nextjs-realworld-example-app/blob/2bbce5199d3a7efa19a3a58426bea25a1cd37579/front/useLoggedInUser.ts
I'll try to minimize it later on.
Another solution: just do SSR
In general, SSR is way simpler than ISR, because you don't have to worry about this get page/ask for data/get data/update page dance from Hell.
ISR is an optimization, and you should only use if there's a proven performance benefit.
Remember that SSR in Next.js is also very data efficient, as Next.js returns only the .json from getServerSideProps on page switches, basically exactly like an API would.
You can then just do authentication from getServerSideProps with cookies, and return the correct page straightaway.
This is how I did it.
const setSession = (accessToken) => {
if (typeof window !== 'undefined')
localStorage.setItem('accessToken', accessToken);
};
const getAccessToken = () => {
if (typeof window !== 'undefined')
return localStorage.getItem('accessToken');
};
Here is where I call them to handle login and to get the access token:
const loginWithEmailAndPassword = async (email, password) => {
const { data } = await axios.post(`${apiUrl}/login`, { email, password });
const { user, accessToken } = data;
if (user) {
setSession(accessToken);
return user;
}
};
const accessToken = getAccessToken();
local storage is not available on the server, there are two options to resolve this
1: create HOC or custom hook to check if the local storage has the data (this is normal react way)
2: you can use cookies to store data on client and server side , which can be then be used getServerSideProps to extract the data and and you can then use this data to display the information accordingly on the initial render.
you can use useEffect hook and useState, so that when component loads, useEffect will fire last, extract data from localStorage and assign it to a STATE from useState.
then you can access your data from useState, states. if that makes sense.
Bottom line, useEffect allows to easily extract data from localStorage, so then you can do what you like with it.
const [userData, setUserData] = useState({});
console.log(userData);
useEffect(()=> {
setUserData(localStorage.getItem('userSession'));
}, [])
The first render which happen on server side can not have access to localStorage and throw the error. To prevent this, add an extra layer of defense with
if (typeof window !== 'undefined') {
// run logic that read/write localStorage
}
Then it should skip the logic when on server and run it when loaded on client side
I have a link on my site. When clicked it'll call a function that does a mongoose query.
I'd like the results of that query to be sent to the same page in a variable without reloading the page. How do I do that? Right now it is just rendering the page again with new query result data.
// List comments for specified chapter id.
commentController.list = function (req, res) {
var chapterId = req.params.chapterId;
var query = { chapterId: chapterId };
Chapter.find({ _id: chapterId }).then(function (chapter) {
var chapter = chapter;
Comment.find(query).then(function (data) {
console.log(chapter);
Chapter.find().then(function(chapters){
return res.render({'chapterlinks', commentList: data, user: req.user, chapterq: chapter, chapters:chapters });
})
});
})
};
You just need to make that request from your browser via AJAX:
https://www.w3schools.com/xml/ajax_intro.asp
This would be in the code for your client (browser), not the code for your server (nodejs).
UPDATE:
Here's a simple example, which uses jQuery to make things easier:
(1) create a function that performs and handles the ajax request
function getChapterLinks(chapterId) {
$.ajax({
url: "/chapterLinks/"+chapterId,
}).done(function(data) {
//here you should do something with data
console.log(data);
});
}
(2) bind that function to a DOM element's click event
$( "a#chapterLinks1" ).click(function() {
getChapterLinks(1);
});
(3) make sure that DOM element is somewhere in you html
<a id="chapterLinks1">Get ChapterLinks 1</a>
Now when this a#chapterLinks1 element is clicked, it will use AJAX to fetch the response of /chaptersLink/1 from your server without reloading the page.
references:
http://api.jquery.com/jquery.ajax/
http://api.jquery.com/jquery.click/
First let me say that sorry if this is a simple question, I'm new to react and express and couldn't find the answer on SO.
I'm trying to pass data to a react object as well as render a view based off of a passport.js return route.
I have the object i need to pass I just can't figure out how to pass it.
First the user hits the auth route
router.get('/steam',
passport.authenticate('steam'),
(req, res) => {
//Not used
});
Then after they login through steam they're returned to this route:
router.get('/steam/return',
passport.authenticate('steam', { failureRedirect: '/' }),
(req, res) => {
res.redirect('/dashboard');
});
From here I'm passing them to the /dashboard route where im taking the user object and creating another call to grab their library and then sending the data to the view:
router.get('/', (req, res, next) => {
var OwnedGamesReqUri = 'http://api.steampowered.com/IPlayerService/GetOwnedGames/v0001/?key=' + process.env.STEAM_API + '&steamid=' + req.user.steamid + '&format=json&include_appinfo=1';
request(OwnedGamesReqUri, (error, response, body) => {
if (!error && response.statusCode == 200) {
var resObj = JSON.parse(body);
//name, playtime_forever, playtime_2weeks, img_icon_url, img_logo_url
res.render('dashboard', { user: req.user, games: resObj.response.games});
}
});
});
I'm able to grab all of the data I need in the dashboard view via handlebars but the problem I'm facing is what I can do to pass the ownedgames data to a react object in another JS file. I have a react component set up in another file that is loaded to the dashboard via a bundle file. I'm assuming this needs to go to the server but I'm just not exactly sure how to achieve this.
Your question isn't about reactjs or passportjs. It's basically how we can pass a variable in server-side javascript to client-side javascript. So you can use that variable in whatever the framework you use in the client-side.
The simplest way to achieve this is rendering your value as variable declaration within an inline script tag in your template. So your client js will have a global variable with that value, which can access from anywhere in your client side scripts.
As an example, if have a variable with string value as follows
var test = 'abc';
You can render it in your template as a variable declaration within a script tag.
res.render('template', test)
template file:
<script>
var test = '{{test}}';
</script>
Now this template will generate an HTML page as follows.
<script>
var test = 'abc';
</script>
So test variable will be a global client side javascript variable with value 'abc', which can access from any other javascript code on the same page.
Even though this is simple as above for a string variable, things get complicated when you are trying to send an object. Because object variables render in the template as [Object object]. To avoid this, you need to send stringify version of your object before sending it the handlebar template.
var data = JSON.stringify({ user: req.user, games: resObj.response.games});
res.render('dashboard', data);
Then your dashboard template needs to have script tag with the variable declaration in addition to its original content.
//...
<script>
var data = {{data}};
</script>
//...
Now, data will be a global variable in your client side and you can use it in your reactjs code to access user and games.
There are several ways to do this, depending on how your React component manages its state.
Reactive state (RxJS, mobx, nx-observe):
The easiest to deal with, your component as well as the non-js code can both access these stores and catch up on the updates together. This provides a very loose coupling between the data provider and consumer.
Component with a flux pattern:
If your component is using Redux, Reflux or any other flux based library to manage state, you can export corresponding actions/functions from your flux code which any JavaScript code can call to update your component's state.
State maintained within the component:
Somewhat messy. In this case your component can export a callback which your script can call to send it new data.
I have a checkbox that when pressed call a function that does a GET request. Based on the selection I want to display extra checkboxes on the same page. At the moment this is the code I have so far:
Client side
function selectedHouse(house)
{
if(house.checked){
$.get('/', {data: house.value});
}
}
Server side
var routing = function (nav, houses) {
router.route('/')
.get(function (req, res) {
var rooms = [];
rooms = getRooms(req.query.data);
console.log(rooms);
res.render('index', {
title: 'Independent cleaner',
nav: nav,
houses: houses,
roomsForHouse: rooms
});
});
return router;
};
The first time the page loads, it loads with the correct title, nav and houses. When the function is executed on client side, I get back the related rooms for the house and I'm trying to populate the roomsForHouse variable which I'm displaying on the view.
The problem is that the view doesn't render the roomsForHouse variable. So the GET request is called once the page loads and a second time when the function executes. Can this be achieved?
It's a bit more complex. You'll need to use ajax for this. EJS is server side templates (as you are using them) so you'll want to use jQuery to make the call and update your already rendered page.
Server
Your server will need a route that delivers JSON data. Right now you are rendering the entire page. So:
app.get('/rooms/:id', function (req, res) {
// Get the house info from database using the id as req.params.id
...
// Return the data
res.json({
rooms: 2
...
});
});
Client
Using jQuery make a call to your json route once the user selects the house.
function selectedHouse(house)
{
if(house.checked){
// Pass some identifier to use for your database
$.ajax({
type: 'GET',
url: '/rooms/' + house.id,
success: function(data) {
// Update the element - easiet is to use EJS to make sure each house has an id/class with the id in it
// Given an ID of 2 this says find the div with class house_2 and updates its div with class room to the number of rooms
$('.house_' + house.id + ' .rooms').text(data.rooms);
});
}
}
This is more of pseudo code then anything but should put you on the right track.
res.render can't rerender view, for refresh page in second time you need use javascript to replace html. This is not good solution
$.get("/",function(html){
document.open();
document.write(html);
document.close();
});
For better you should use another router to render DOM you want to change