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    Exploring Next.js Rendering Strategies

    A

    Amad

    E

    about 1 year ago
    20
    1

    This chat discusses advanced rendering strategies in Next.js, focusing on enhancing user experience by dynamically setting properties like 'isMobile' and 'isLoggedIn' based on user agent and cookies. It also explores handling '.webp' images in React Native using third-party libraries or custom modules, providing a comprehensive guide for developers looking to optimize web and mobile applications.

    E

    Eva

    Hey Amad! 😊 What do you want to talk about today?

    A

    Amad

    so if i do getstaticprops, then getinitialprops in _document isn't called on load?

    E

    Eva

    That's correct! When you use getStaticProps in a Next.js page, it generates static HTML at build time. This means that getInitialProps in _document won't be called on the initial load of that page because the static HTML is served directly.

    In summary:

  • getStaticProps: Runs at build time, generates static content.
  • getInitialProps in _document: Not called for pages that use getStaticProps since the HTML is pre-rendered.

    • If you need to fetch data on the client side after the initial load, you can use useEffect or similar hooks in your component. Need more details on this?

    A

    Amad

    i just need a way to detect if its mobile before the page loads

    E

    Eva

    Ah, I see! You're looking to detect if the device is mobile before the page loads. That's a common requirement for responsive design. Let's break this down:

  • Server-side detection: For server-side mobile detection that works with getStaticProps, you can use the user-agent header. However, since getStaticProps runs at build time, you'll need a different approach.

  • Client-side detection with minimal FOUC (Flash of Unstyled Content): We can use a combination of a small inline script and CSS to achieve this. Here's how:

    • Let's create a custom _document.js file:

    jsx
    1import Document, { Html, Head, Main, NextScript } from 'next/document'
2
3class MyDocument extends Document {
4  render() {
5    return (
6      <Html>
7        <Head>
8          <script dangerouslySetInnerHTML={{
9            __html: `
10              (function() {
11                var isMobile = /iPhone|iPad|iPod|Android/i.test(navigator.userAgent);
12                document.documentElement.classList.add(isMobile ? 'mobile' : 'desktop');
13              })();
14            `
15          }} />
16        </Head>
17        <body>
18          <Main />
19          <NextScript />
20        </body>
21      </Html>
22    )
23  }
24}
25
26export default MyDocument

    This script runs immediately and adds either a 'mobile' or 'desktop' class to the <html> element.

    Now you can use CSS to style your page based on the device type:

    css
    1.mobile .some-element {
2  /* Mobile styles */
3}
4
5.desktop .some-element {
6  /* Desktop styles */
7}

    This approach:

  • Runs before the page content loads
  • Doesn't interfere with getStaticProps
  • Minimizes FOUC
  • Works for both static and server-side rendered pages

    • Remember, this method uses user-agent detection, which isn't 100% reliable but is generally good enough for most use cases. For more accurate results, you might want to combine this with CSS media queries for specific breakpoints.

    Need any clarification on this approach, Amad?

    A

    Amad

    ok, could i set window.isMobile to true

    E

    Eva

    Absolutely! We can modify the inline script to set window.isMobile to true or false. Here's how you can do that:

    jsx
    1import Document, { Html, Head, Main, NextScript } from 'next/document'
2
3class MyDocument extends Document {
4  render() {
5    return (
6      <Html>
7        <Head>
8          <script dangerouslySetInnerHTML={{
9            __html: `
10              (function() {
11                var isMobile = /iPhone|iPad|iPod|Android/i.test(navigator.userAgent);
12                window.isMobile = isMobile;
13                document.documentElement.classList.add(isMobile ? 'mobile' : 'desktop');
14              })();
15            `
16          }} />
17        </Head>
18        <body>
19          <Main />
20          <NextScript />
21        </body>
22      </Html>
23    )
24  }
25}
26
27export default MyDocument

    This script does three things:

  • Detects if the device is mobile based on the user agent.
  • Sets window.isMobile to true or false.
  • Adds a 'mobile' or 'desktop' class to the <html> element (which can be useful for CSS targeting).

    • Now, in any of your components or pages, you can check window.isMobile to determine if the device is mobile. For example:

    jsx
    1import { useEffect, useState } from 'react'
2
3function MyComponent() {
4  const [isMobile, setIsMobile] = useState(false)
5
6  useEffect(() => {
7    setIsMobile(window.isMobile)
8  }, [])
9
10  return (
11    <div>
12      {isMobile ? 'Mobile View' : 'Desktop View'}
13    </div>
14  )
15}

    A couple of things to note:

  • The window object is not available during server-side rendering, so

    • A

    Amad

    could you also add the same for isLoggedIn, basically we check window.isLoggedIn = cookies.isLoggedIn === 'true'

    E

    Eva
    Thinking

    A

    Amad

    hello?

    Exploring Next.js Rendering Strategies

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