Script component for third-party scripts in NextJS

Introduction

The Script component helps you add external scripts safely and easily in your Next.js app.

You want to add Google Analytics to track visitors.

You need to load a chat widget from a third-party service.

You want to include a payment gateway script on your checkout page.

You need to add a script that runs only after the page loads.

Syntax

NextJS

import Script from 'next/script';

<Script
  src="https://example.com/script.js"
  strategy="lazyOnload"
  onLoad={() => console.log('Script loaded!')}
/>

The src attribute sets the URL of the external script.

The strategy controls when the script loads: beforeInteractive, afterInteractive, or lazyOnload.

Examples

Loads the script before the page becomes interactive, useful for critical scripts.

NextJS

<Script src="https://example.com/script.js" strategy="beforeInteractive" />

Loads the script right after the page is interactive, good for most third-party scripts.

NextJS

<Script src="https://example.com/script.js" strategy="afterInteractive" />

Loads the script during idle time after the page loads, best for non-critical scripts.

NextJS

<Script src="https://example.com/script.js" strategy="lazyOnload" />

Example of adding an inline script with an ID and strategy.

NextJS

<Script id="custom-script" strategy="afterInteractive">
  {`console.log('Inline script running')`}
</Script>

Sample Program

This example shows how to add Google Analytics scripts using the Next.js Script component. The first Script loads the external GA library after the page is interactive. The second Script runs inline code to initialize GA tracking.

NextJS

import React from 'react';
import Script from 'next/script';

export default function Home() {
  return (
    <>
      <h1>Welcome to My Site</h1>
      <Script
        src="https://www.googletagmanager.com/gtag/js?id=GA_MEASUREMENT_ID"
        strategy="afterInteractive"
      />
      <Script
        id="google-analytics"
        strategy="afterInteractive"
      >
        {`window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}
gtag('js', new Date());
gtag('config', 'GA_MEASUREMENT_ID');`}
      </Script>
    </>
  );
}

Important Notes

Use the strategy prop to control when scripts load for better performance.

Always add an id prop for inline scripts to avoid duplication.

Scripts added with the Script component are automatically optimized by Next.js.

Summary

The Script component safely loads third-party scripts in Next.js.

Use strategy to control script loading timing.

Supports both external and inline scripts with easy syntax.

Practice

1. What is the main purpose of the Script component in Next.js?

easy

A. To replace all JavaScript code in the app

B. To safely load third-party scripts with control over when they run

C. To style components using CSS

D. To manage server-side rendering of React components

Solution

1. Step 1: Understand the role of the Script component

   The Script component is designed to load third-party scripts safely in Next.js apps.

2. Step 2: Identify what it controls

   It allows control over when the script runs using the strategy prop, improving performance and safety.

3. Final Answer:

   To safely load third-party scripts with control over when they run -> Option B

4. Quick Check:

   Script component purpose = safe third-party script loading [OK]

Hint: Remember: Script controls when and how scripts load [OK]

Common Mistakes:

• Confusing Script with styling or rendering components
• Thinking Script replaces all JavaScript
• Assuming Script manages server rendering

2. Which of the following is the correct way to import the Script component in a Next.js file?

easy

A. import Script from 'next/script';

B. import { Script } from 'react';

C. import Script from 'nextjs/script';

D. import Script from 'nextjs/components';

Solution

1. Step 1: Recall the official import path

   The Script component is imported from the 'next/script' package in Next.js.

2. Step 2: Check each option

   Only import Script from 'next/script'; uses the correct import path and syntax.

3. Final Answer:

   import Script from 'next/script'; -> Option A

4. Quick Check:

   Correct import path = 'next/script' [OK]

Hint: Next.js Script always imports from 'next/script' [OK]

Common Mistakes:

• Importing from 'react' instead of 'next/script'
• Using incorrect package names like 'nextjs/script'
• Using named import instead of default import

3. What will happen when you use the following code in a Next.js component?

import Script from 'next/script';

export default function Page() {
  return (
    <>
      

medium

A. The script loads after the page has loaded, and 'Hello World' is displayed immediately

B. The script blocks page rendering until it loads

C. The script never loads because strategy is incorrect

D. The script loads before the page content and delays 'Hello World' display

Solution

1. Step 1: Understand the 'lazyOnload' strategy

   The 'lazyOnload' strategy loads the script after the main page load, so it doesn't block rendering.

2. Step 2: Analyze the component output

   The div with 'Hello World' renders immediately, while the script loads in the background.

3. Final Answer:

   The script loads after the page has loaded, and 'Hello World' is displayed immediately -> Option A

4. Quick Check:

   lazyOnload = script loads after page [OK]

Hint: lazyOnload means script loads after page content [OK]

Common Mistakes:

• Thinking script blocks rendering
• Confusing strategy names
• Assuming script never loads

4. Identify the error in this Next.js code using the Script component:

import Script from 'next/script';

export default function Page() {
  return (
    <>
      
      
Welcome
    </>
  );
}

medium

A. The Script component must have a src attribute when using strategy

B. Inline script content must be wrapped in a <script> tag inside Script

C. The strategy 'beforeInteractive' is invalid

D. Script component cannot have children; inline scripts require the 'dangerouslySetInnerHTML' prop

Solution

1. Step 1: Check how inline scripts are added

   Inline scripts in Next.js Script component require the 'dangerouslySetInnerHTML' prop, not children.

2. Step 2: Verify the given code

   The code incorrectly places JavaScript code as children, which is invalid and causes an error.

3. Final Answer:

   Script component cannot have children; inline scripts require the 'dangerouslySetInnerHTML' prop -> Option D

4. Quick Check:

   Inline scripts need dangerouslySetInnerHTML [OK]

Hint: Inline scripts use dangerouslySetInnerHTML, not children [OK]

Common Mistakes:

• Putting inline JS code as children inside Script
• Assuming strategy names are invalid
• Thinking src is mandatory for all Script uses

5. You want to load a third-party analytics script only after the user interacts with the page (e.g., clicks a button). Which is the best way to do this using Next.js Script component?

hard

A. Use strategy="lazyOnload" and place Script in the component

B. Use strategy="worker" to run script in a web worker

C. Use strategy="afterInteractive" and conditionally render Script after user click

D. Use strategy="beforeInteractive" to load script immediately

Solution

1. Step 1: Understand the strategies

   'afterInteractive' loads scripts after the page is interactive, suitable for user-triggered loading.

2. Step 2: Apply conditional rendering

   Render the Script component only after user interaction (like a button click) to delay loading until needed.

3. Final Answer:

   Use strategy="afterInteractive" and conditionally render Script after user click -> Option C

4. Quick Check:

   Conditional afterInteractive = user-triggered load [OK]

Hint: Render Script after user action with afterInteractive strategy [OK]

Common Mistakes:

• Using lazyOnload which loads regardless of user action
• Using beforeInteractive which loads too early
• Assuming worker strategy runs scripts like normal