our app need to do around 37000 pages generation with an array generated by getStaticPath
the getStaticProps need to do a request on our api for build each page, but we have currently some timeout request.
Then, i will try to add a little timer in each request (i think about 0.1 second) but i didn't find anywhere a nextjs parameter to do this
Anyone allready do this?
Ok so for your case I think you should use getServerSideProps, you told that you need Dynamic SEO for each page and that is exactly what getServerSideProps id for, the idea is to render specific meta that depend on the data you get from your request, here is an example below:
export const getServerSideProps = async (context) => {
try {
let { data } = await axios.get("YOUR_URL")
return {
props: {
data,
},
}
} catch (e) {
console.log(e)
}
}
And in your component
<Head>
<link rel="canonical" href={canonicalUrl} />
<title>{title}</title>
<meta name="title" content={data.productTitle} />
<meta name="description" content={data.description} />
...etc
</Head>
Related
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.
I have made a login system with jwt and, basically, the user redirects to the homepage (homepage/) if login (homepage/login) is successfull. After that, even if the user types (homepage/login) in the url, they get redirected back to the homepage because (and as long as) they have the jwt token.
I have the following code:
app.get('/login', (req, res) => {
const token = req.cookies.jwt
if(token) {
res.redirect('/')
} else {
res.render('login')
}
})
HOWEVER, if the user goes to (homepage/login) through the "back button", they are no longer redirected even though they have the token.
How can I include a redirect if the back button is pressed ?
Redirection is happening on client side.
So, simply include a frontend javascript code that checks if token is there. If not present, redirect.
In html code, include this script in head tag (assuming you are using localstorage to store token:
<html>
<head>
..
..
<script>
const token = localstorage.getItem("token");
if(token == null) {
window.location.replace("-path-to-home-page-");
}
</script>
</head>
<body>
..
..
..
</body>
</html>
I have two different versions of an endpoint for testing.
The first one is this:
app.get('/order', async (req, res) => {
console.log("OK")
getPrintFile()
})
And the second one is this:
app.get('/order', async (req, res) => {
console.log("OK")
await getPrintFile()
})
the getPrintFile is an async function that returns a promise when every operation is done. Withing the function I upload an image to a
server, I download a new image, and re upload that new image to another server.
I noticed that in the first example, without the await, if I send a lot of requests to the "order" endpoint,
I get the "OK" instantly for each request, which is what I want because that "OK" will get replaced by a res.status("200"). I need
to send a status 200 immediatly after getting the endpoint hit for various reasons. Then I don't care how long it takes for the server to do all the processing of the images/uploading, as long as the res.send(200) is executed instantly when there is a new incoming request.
However, when I use the await, even if new requests are coming in, it takes a lot to display the next "OK" if a previous request
is still processing. Usually it displays the OK only when the code within the getPrintFile function is done executing (that is, images are uploaded and everything is done)
It's like the event loop is blocked but I don't understand why.
What is happening here?
Edit:
So it is clearer, I tested it. If I send 5 requests to the "order" endpoint, the "OK" is displayed in the console immediately for all of them, and then the images are processed and uploaded at their own speed for each request. In the second example, if I send 5 requests, the first OK is displayed, and then the remaining 4 are displayed one at a time when the previous request is done executing, or if not exactly in that order, they get logged with tremendous delay, and not consecutively
I'll try to answer based on my understanding of your problem. The first thing missing is the res.sendStatus(200) in your examples to make them actually work. But then, indeed it happens as you describe it: the /order endpoint actually is "blocking" you from making another request as the await is blocking you from reaching the final statement (res.send). Here a full example
const express = require("express");
const app = express();
async function takeTime() {
return new Promise((resolve, reject) => {
setTimeout(() => {
console.log("resolved");
resolve(1);
}, 2000);
});
}
app.get("/order", (req, res) => {
console.log("ok"); // Happens immediately
await takeTime();
return res.sendStatus(200);
});
app.get("/", async (req, res) => {
console.log("ok"); // Happens immediately
takeTime();
return res.sendStatus(200);
});
app.listen(3000, () => {
console.log("server running on port 3000");
});
When testing the API (i.e. from Postman), you won't be able to run immediately another request on the /order endpoint, because you will be locked in waiting for the answer of the request just sent.
In the / endpoint, on the other hand, you will receive immediately the HTTP 200 response (as there is no await) and the code for the takeTime function will keep running asynchronously until it's done.
Here you can find more information, I hope it's useful.
Edit 1
here I add the .html page I'm using to test the await loop requests
<!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" />
<title>Document</title>
</head>
<body></body>
<script>
for (let i = 0; i < 10; i++) {
fetch("http://localhost:3000/order");
}
</script>
</html>
The fetch is not working for me in the browser, but having a web page making those request works
I am wondering how to get "visual" DOM structure from url in node.js. When I try to get html content with request library, html structure is not correct.
const request = require('request');
const jsdom = require("jsdom");
const { JSDOM } = jsdom;
request({ 'https://www.washingtonpost.com/news/acts-of-faith/wp/2017/06/30/trump-promised-to-destroy-the-johnson-amendment-congress-is-targeting-it-now/', jar: true }, function (e, r, body) {
console.log(body);
});
reurned html structure is here, where meta tags are not correct:
<meta property="og:title" content=""/>
<meta itemprop="description" name="description" content=""/>
If I open website in web browser, I can see correct meta tags in web inspector:
<meta property="og:title" content="Trump promised to destroy the Johnson Amendment. Congress is targeting it now."/>
<meta itemprop="description" name="description" content="Observers believe the proposed legislation would make it harder for the IRS to enforce a law preventing pulpit endorsements."/>
I might need more clarification on what a "visual" DOM structure is, but as a commenter pointed out a headless browser like puppeteer is probably the way to go when a website has complex loading behavior.
The advantage here is, with puppeteer at least, you can navigate to a page and then programmatically wait until some condition is satisfied before continuing. In this case, I chose to wait until one of the meta tags you specified's content attribute is truthy, but depending on your needs you could wait for something else or even wait for multiple conditions to be true.
You might have to analyze the behavior of the page in question a little deeper to figure out what you should wait for though, but at the very least the following code seems to correctly load the tags in your question.
import puppeteer from 'puppeteer'
(async ()=>{
const url = 'https://www.washingtonpost.com/news/acts-of-faith/wp/2017/06/30/trump-promised-to-destroy-the-johnson-amendment-congress-is-targeting-it-now/'
const browser = await puppeteer.launch()
const page = await browser.newPage()
await page.goto(url)
// wait until <meta property="og:title"> has a truthy value for content attribute
await page.waitForFunction(()=>{
return document.querySelector('meta[property="og:title"]').getAttribute('content')
})
const html = await page.content()
console.log(html)
await browser.close()
})()
(pastebin of formatted html result)
Also, since this solution uses puppeteer I'd recommend not working with the html string and instead using the puppeteer API to extract the information you need.
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