Subsequent.js has 5 kinds of data-fetching patterns for figuring out the way you need content material to be seen in your software: static-site era (SSG), server-side rendering (SSR), client-side rendering (CSR), incremental static regeneration (ISR), and dynamic routing.
You’ll be able to select whichever of those patterns that fits the construction of your software. To be taught extra about these patterns, examine them within the official documentation.
This text focuses on static-site era and dynamic routing. Utilizing these patterns requires the usage of the getStaticProps and getStaticPaths data-fetching strategies. These strategies play distinctive roles in acquiring knowledge.
We’ve been speaking about dynamic knowledge for some time now. Let’s perceive what that really means.
Say we’ve a listing of customers in an software being rendered on an internet web page, and we need to get data distinctive to a consumer once we click on on their title — the knowledge we get would change in accordance with the motion we carry out (clicking on the consumer’s title).
We would like a approach to render that knowledge on a singular web page (or display screen) within the software, and the getStaticPaths data-fetching technique permits us to acquire knowledge that’s distinctive to a consumer. That is often frequent in an array of consumer objects with a singular key (id or _id), relying on how the response object is structured.
export async perform getStaticPaths() {
return {
paths: {
[{
params: {
uniqueId: id.toString()
}
}],
fallback: false
}
}
}
The distinctive key obtained from the getStaticPaths technique (generally known as the parameter, or params for brief) is handed as an argument by the context parameter in getStaticProps.
This brings us again to the truth that getStaticPaths can’t work with out getStaticProps. Each of them perform collectively, since you’ll have to go the distinctive id from the statically generated path as an argument to the context parameter in getStaticProps. The code snippet beneath illustrates this:
export async perform getStaticProps(context) {
return {
props: {
userData: knowledge,
},
}
}
The Cons of Utilizing the Native Knowledge-Fetching Strategies Of Subsequent.js
Now that we perceive a little bit about dynamic data-fetching in Subsequent.js, let’s have a look at the cons of utilizing the 2 aforementioned data-fetching strategies.
Getting knowledge from a public API that requires no authorization with some form of API key throughout data-fetching could be completed with getStaticProps and getStaticPaths.
Check out each of them beneath:
// getStaticPaths
export async perform getStaticPaths() {
const response = fetch(“https://jsonplaceholder.typicode.com/customers”)
const userData = await response.json()
// Getting the distinctive key of the consumer from the response
// with the map technique of JavaScript.
const uniqueId = userData.map((knowledge) => {
return knowledge.id
})
return {
paths: {
[{
params: {
uniqueId: uniqueId.toString()
}
}],
fallback: false
}
}
}
You’ll discover that the distinctive id is gotten from the map technique of JavaScript, and we’re going to assign it as a price by the context parameter of getStaticProps.
// Receive the consumer’s distinctive ID.
const userId = context.params.uniqueId
// Append the ID as a parameter to the API endpoint.
const response = fetch(https://jsonplaceholder.typicode.com/customers/${userId})
const userData = await response.json()
return {
props: {
userData,
},
}
}
Within the snippet above, you’ll see {that a} variable named userId was initialized, and its worth was gotten from the context parameter.
That worth is then added as a parameter to the bottom URL of the API.
Observe: The getStaticProps and getStaticPaths data-fetching strategies could solely be exported from a file within the pages folder of Subsequent.js.
That just about does it for a public API. However while you’re constructing an software that requires the consumer to log in, sign off, and maybe carry out some data-fetching within the software after they log in with their account, the applying stream is completely different.
Fetching Knowledge in an Authenticated System.
The stream of acquiring knowledge in an authenticated system is sort of completely different from the traditional approach we get knowledge from a public API.
Image this state of affairs: A consumer logs into an internet app after which visits their profile. On their profile web page (as soon as it’s rendered), they’re in a position to see and alter the knowledge that they offered when signing up.
For this to occur, there needs to be some form of verification of the information that’s being despatched to the consumer by the developer who constructed the interface. Fortunately, there’s a standard sample for authorizing a consumer after they log right into a system: JSON Net Tokens (JWTs).
When a consumer indicators up to make use of your software for the primary time, their particulars are saved within the database, and a singular JWT is assigned to that consumer’s schema (relying on how the back-end API has been designed).
When the consumer tries to log into your app, and their credentials match what they initially signed up with, the following factor we front-end engineers should do is present an authentication state for the consumer, in order that we will get hold of the required particulars, considered one of which is the JWT.
There are completely different colleges of thought on tips on how to protect a consumer’s auth-state, together with utilizing Redux, Composition in React, and React’s Context API (I’d suggest the Context API). Átila Fassina’s article goes over state-management paradigms in Subsequent.js.
The frequent strategy is to retailer the JWT in localStorage — to get began no less than, if we’re contemplating the difficulty of safety in a strict method. Storing your JWT in an httpOnly cookie is advisable, to stop safety assaults resembling a cross-site request forgery (CSRF) and cross-site scripting (XSS).
As soon as once more, this strategy can solely be potential if the suitable cookie middleware is offered within the API that the back-end engineers have constructed.
In the event you don’t need to undergo the trouble of determining how the back-end engineers have designed an API, an alternate path to authentication in Subsequent.js is to utilize the open-source authentication challenge NextAuth.js.
As soon as the token is in localStorage on the shopper aspect, the API calls that require the consumer token as a way of authorization can undergo, with out throwing a 501 (unauthorized) error.
headers: {
“x-auth-token”: localStorage.getItem(“token”)
}
Knowledge-Fetching With the useRouter Hook
Within the first part, we noticed how the method of dynamic data-fetching works in Subsequent.js for an software that doesn’t require authentication.
On this part, we’ll have a look at tips on how to bypass the difficulty of the getStaticProps and getStaticPaths data-fetching strategies throwing a referenceError (“localStorage is undefined”) once we attempt to get the consumer’s token from localStorage.
This error happens as a result of the 2 data-fetching strategies are at all times working on the server within the background, which, in flip, makes the localStorage object unavailable to them, as a result of it’s on the shopper aspect (within the browser).
The router API of Subsequent.js creates plenty of potentialities once we we’re coping with dynamic routes and knowledge. With the useRouter hook, we must always have the ability to get knowledge that’s distinctive to a consumer primarily based on their distinctive ID.
Let’s have a look at the snippet beneath to get began:
// pages/index.js
import React from “react”;
import axios from “axios”;
import { userEndpoints } from “../../../routes/endpoints”;
import Hyperlink from “subsequent/hyperlink”;
const Customers = () => {
const [data, setData] = React.useState([])
const [loading, setLoading] = React.useState(false)
const getAllUsers = async () => {
strive {
setLoading(true);
const response = await axios({
technique: “GET”,
url: userEndpoints.getUsers,
headers: {
“x-auth-token”: localStorage.getItem(“token”),
“Content material-Sort”: “software/json”,
},
});
const { knowledge } = response.knowledge;
setData(knowledge);
} catch (error) {
setLoading(false);
console.log(error);
}
};
return (
<React.Fragment>
<p>Customers record</p>
{knowledge.map((consumer) => {
return (
<Hyperlink href={`/${consumer._id}`} key={consumer._id}>
<div className=”consumer”>
<p className=”fullname”>{consumer.title}</p>
<p className=”place”>{consumer.function}</p>
</div>
</Hyperlink>
);
})}
</React.Fragment>
);
};
export default Customers;
Within the snippet above, we’ve used the useEffect hook to get the information as soon as the web page is rendered for the primary time. You’ll additionally discover that the JWT is assigned to the x-auth-token key within the request header.
After we click on on a consumer, the Hyperlink part will route us to a brand new web page primarily based on the consumer’s distinctive ID. As soon as we’re on that web page, we need to render the knowledge that’s particularly accessible for that consumer with the id.
The useRouter hook provides us entry to the pathname within the URL tab of the browser. With that in place, we will get the question parameter of that distinctive route, which is the id.
The snippet beneath illustrates the entire course of:
// [id].js
import React from “react”;
import Head from “subsequent/head”;
import axios from “axios”;
import { userEndpoints } from “../../../routes/endpoints”;
import { useRouter } from “subsequent/router”;
const UniqueUser = () => {
const [user, setUser] = React.useState({
fullName: “”,
e-mail: “”,
function: “”,
});
const [loading, setLoading] = React.useState(false);
const { question } = useRouter();
// Acquiring the consumer’s distinctive ID with Subsequent.js’
// useRouter hook.
const currentUserId = question.id;
const getUniqueUser = async () => {
strive {
setLoading(true);
const response = await axios({
technique: “GET”,
url: `${userEndpoints.getUsers}/${currentUserId}`,
headers: {
“Content material-Sort”: “software/json”,
“x-auth-token”: localStorage.getItem(“token”),
},
});
const { knowledge } = response.knowledge;
setUser(knowledge);
} catch (error) {
setLoading(false);
console.log(error);
}
};
React.useEffect(() => {
getUniqueUser();
}, []);
return (
<React.Fragment>
<Head>
<title>
{`${consumer.fullName}’s Profile | “Profile” `}
</title>
</Head>
<div>
<div className=”user-info”>
<div className=”user-details”>
<p className=”fullname”>{consumer.fullName}</p>
<p className=”function”>{consumer.function}</p>
<p className=”e-mail”>{consumer.e-mail}</p>
</div>
</div>
</div>
)}
</React.Fragment>
);
};
export default UniqueUser;
Within the snippet above, you’ll see that we’ve destructured the question object from the useRouter hook, which we’ll be utilizing to get the consumer’s distinctive ID and go it as an argument to the API endpoint.
const {question} = useRouter()
const userId = question.id
As soon as the distinctive ID is appended to the API endpoint, the information that’s meant for that consumer will probably be rendered as soon as the web page is loaded.
Conclusion
Knowledge-fetching in Subsequent.js can get difficult in case you don’t totally perceive the use case of your software.
I hope this text has helped you perceive tips on how to use the router API of Subsequent.js to get dynamic knowledge in your purposes.
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