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Hooks are a new addition in React that lets you use state and other React features without writing a class. This website provides easy to understand code examples to help you learn how hooks work and inspire you to take advantage of them in your next project.

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useLockBodyScroll

Sometimes you want to prevent your users from being able to scroll the body of your page while a particular component is absolutely positioned over your page (think modal or full-screen mobile menu). It can be confusing to see the background content scroll underneath a modal, especially if you intended to scroll an area within the modal. Well, this hook solves that! Simply call the useLockBodyScroll hook in any component and body scrolling will be locked until that component unmounts. See it in action in the CodeSandbox Demo.

import { useState, useLayoutEffect } from "react";

// Usage
function App() {
  // State for our modal
  const [modalOpen, setModalOpen] = useState(false);

  return (
    <div>
      <button onClick={() => setModalOpen(true)}>Show Modal</button>
      <Content />
      {modalOpen && (
        <Modal
          title="Try scrolling"
          content="I bet you you can't! Muahahaha 😈"
          onClose={() => setModalOpen(false)}
        />
      )}
    </div>
  );
}

function Modal({ title, content, onClose }) {
  // Call hook to lock body scroll
  useLockBodyScroll();

  return (
    <div className="modal-overlay" onClick={onClose}>
      <div className="modal">
        <h2>{title}</h2>
        <p>{content}</p>
      </div>
    </div>
  );
}

// Hook
function useLockBodyScroll() {
  useLayoutEffect(() => {
    // Get original body overflow
    const originalStyle = window.getComputedStyle(document.body).overflow;
    // Prevent scrolling on mount
    document.body.style.overflow = "hidden";
    // Re-enable scrolling when component unmounts
    return () => (document.body.style.overflow = originalStyle);
  }, []); // Empty array ensures effect is only run on mount and unmount
}
import { useState, useLayoutEffect } from "react";

// Usage
function App() {
  // State for our modal
  const [modalOpen, setModalOpen] = useState<boolean>(false);

  return (
    <div>
      <button onClick={() => setModalOpen(true)}>Show Modal</button>
      <Content />
      {modalOpen && (
        <Modal
          title="Try scrolling"
          content="I bet you you can't! Muahahaha 😈"
          onClose={() => setModalOpen(false)}
        />
      )}
    </div>
  );
}


// Define modal props type
type ModalProps = {
  title: string;
  content: string;
  onClose: () => void;
}

function Modal({ title, content, onClose } : ModalProps) {
  // Call hook to lock body scroll
  useLockBodyScroll();

  return (
    <div className="modal-overlay" onClick={onClose}>
      <div className="modal">
        <h2>{title}</h2>
        <p>{content}</p>
      </div>
    </div>
  );
}

// Hook
function useLockBodyScroll(): void {
  // useLaoutEffect callback return type is "() => void" type
  useLayoutEffect(() : () => void => {
    // Get original body overflow
    const originalStyle: string = window.getComputedStyle(document.body).overflow;
    // Prevent scrolling on mount
    document.body.style.overflow = "hidden";
    // Re-enable scrolling when component unmounts
    return () => (document.body.style.overflow = originalStyle);
  }, []); // Empty array ensures effect is only run on mount and unmount
}
January 15, 2019
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