Building a Universal "Scroll-To" Hook in React & Next.js

On a landing page, navigation usually involves smooth scrolling to sections. However, once you add multiple pages (like a Blog or FAQ), a simple element.scrollIntoView() isn't enough. You need a way to navigate back to the home page and then scroll to the section.

The Math Behind the Scroll

To get the exact position for window.scrollTo, we use a specific formula. Think of it like finding a specific page in a book:

1. getBoundingClientRect().top: How far the element is from the current top of your screen.

2. window.scrollY: How far you have already scrolled down the page.

3. offset: Space for your sticky header so it doesn't cover the section title.

The Formula: Target = Viewport Top + Current Scroll - Offset

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The Implementation: useScrollTo

This hook handles three scenarios:

1. External Links: Redirects normally.

2. Same-page Scroll: Scrolls smoothly and updates the URL hash.

3. Cross-page Scroll: Navigates to the correct page first, then scrolls after the page loads.

JavaScript

import { useRouter } from "next/router";

/**
 * A universal hook for smooth scrolling that handles 
 * both same-page and cross-page navigation.
 */
export function useScrollTo() {
  const router = useRouter();

  const scrollTo = (href, offset = 0) => {
    if (typeof window === "undefined") return;

    // 1. Handle External Links
    if (href.startsWith("http")) {
      window.location.href = href;
      return;
    }

    const targetId = href.startsWith("#") ? href.substring(1) : href;
    const targetElement = document.getElementById(targetId);

    // 2. Scenario: Element exists on current page
    if (targetElement) {
      const targetPosition =
        targetElement.getBoundingClientRect().top + window.scrollY - offset;
      
      window.scrollTo({ top: targetPosition, behavior: "smooth" });
      
      // Update URL hash without a full page refresh
      window.history.pushState(null, "", `#${targetId}`);
    } 
    // 3. Scenario: Element is on a different page
    else {
      // Navigate to the root (or specific page) with the hash
      router.push(`/#${targetId}`).then(() => {
        // Wait briefly for the new page to mount
        setTimeout(() => {
          const newTarget = document.getElementById(targetId);
          if (newTarget) {
            const newPos = newTarget.getBoundingClientRect().top + window.scrollY - offset;
            window.scrollTo({ top: newPos, behavior: "smooth" });
          }
        }, 150);
      });
    }
  };

  return scrollTo;
}

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How to Use It

Simply call the hook in your component and pass the ID of the section you want to reach.

JavaScript

const scrollTo = useScrollTo();

<Button onClick={() => scrollTo("pricing-section", 80)}>
  View Pricing
</Button>

Why This Approach is Better:

• URL Synchronicity: It uses window.history.pushState. If the user refreshes or shares the link, the #id stays in the URL, allowing the browser to find the spot again.

• The "Header Gap" Fix: Most landing pages have a sticky navbar. By passing an offset, you prevent the navbar from overlapping your section headings.

• Next.js Integration: Using router.push().then() ensures that we only attempt to scroll after Next.js has finished the route transition.

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Pro-Tip: Why the setTimeout?

In the cross-page scenario, we use a small delay (100ms–150ms). This is because Next.js needs a split second to render the DOM elements on the new page before document.getElementById can actually find them.