Understanding the Example Codes

Understanding the Concepts:

• Viewport: The visible area of a web page within a browser window.
• Window: The browser window itself.
• ReactJS: A JavaScript library for building user interfaces.

Methods to Get Viewport/Window Height:

Key Points:

• Use window.innerHeight to get the viewport height.
• Employ the useEffect hook in React to handle window resize events and update the state accordingly.
• Remember to clean up the event listener in the useEffect cleanup function to avoid memory leaks.

Understanding the Example Codes

Key Concepts:

• useEffect hook: Used to perform side effects in React components, such as fetching data or setting up event listeners.
• State management: Using the useState hook to manage the component's state and trigger re-renders when the state changes.
• window.innerHeight: Returns the height of the viewport (the visible area of the browser window) in pixels.

Example 1: Using window.innerHeight directly:

import React, { useState, useEffect } from 'react';

function MyComponent() {
  const [viewportHeight, setViewportHeight] = useState(window.innerHeight);

  useEffect(() => {
    const handleResize = () => {
      setViewportHeight(window.innerHeight);
    };

    window.addEventListener('resize', handleResize);   

    return () => {
      window.removeEventListener('resize', handleResize);
    };
  }, []);

  return    (
    <div>
      Viewport Height: {viewportHeight} pixels
    </div>
  );
}

Explanation:

1. State initialization: The viewportHeight state is initialized with the initial viewport height.
2. useEffect hook:
   • Adds an event listener for the resize event on the window object.
   • Updates the viewportHeight state whenever the window is resized.
   • Cleans up the event listener in the cleanup function to prevent memory leaks.
3. Rendering: The viewportHeight value is rendered in the component's JSX.

Example 2: Using a custom hook:

import { useState, useEffect } from 'react';

function useWindowDimensions() {
  const [windowSize, setWindowSize] = useState({
    width: undefined,
    height: undefined,
  });

  useEffect(() => {
    const handleResize    = () => {
      setWindowSize({
        width: window.innerWidth,
        height: window.innerHeight,
      });
    };

    window.addEventListener('resize', handleResize);

    handleResize();    // Set initial values

    return () => {
      window.removeEventListener('resize', handleResize);   
    };
  }, []);

  return windowSize;
}

function MyComponent() {
  const { height } = useWindowDimensions();

  return (
    <div>
      Viewport Height: {height} pixels
    </div>
  );
}

1. Custom hook: The useWindowDimensions hook encapsulates the logic for getting and updating window dimensions.
2. State management: The hook manages the windowSize state, which includes both width and height.
3. Event listener: The hook adds a resize event listener and updates the state accordingly.
4. Component usage: The MyComponent uses the useWindowDimensions hook to access the height property and render it.

Alternative Methods for Getting Viewport/Window Height in ReactJS

While the methods described in previous responses are common approaches, here are some alternative techniques you can consider:

Using a Third-Party Library:

• React Window Dimensions: This library provides a convenient hook to access window dimensions, including height and width.
• React Breakpoints: While primarily designed for media queries, it also offers a useBreakpoint hook that can be used to determine viewport dimensions.

Leveraging CSS Custom Properties (CSS Variables):

• Dynamically set CSS variables: Use JavaScript to set CSS variables based on window dimensions.
• Access CSS variables in React: Access these variables in your React components using window.getComputedStyle or a CSS-in-JS library.

Using a Window Dimensions Context Provider:

• Create a context: Create a context to store and share window dimensions throughout your application.
• Provide the context: Wrap your application's root component with the context provider.
• Consume the context: Use the useContext hook in components that need access to window dimensions.

Example using a Third-Party Library (React Window Dimensions):

import React, { useState, useEffect } from 'react';
import useWindowDimensions from 'react-window-dimensions';

function MyComponent() {
  const { height } = useWindowDimensions();

  return (
    <div>
      Viewport Height: {height} pixels
    </div>
  );
}

Example using CSS Custom Properties:

import React, { useEffect } from 'react';

function MyComponent() {
  useEffect(() => {
    const root = document.documentElement;
    root.style.setProperty('--viewport-height', `${window.innerHeight}px`);
  }, []);

  return (
    <div>
      Viewport Height: var(--viewport-height)
    </div>
  );
}

Example using a Context Provider:

import React, { createContext, useState, useEffect } from 'react';

const WindowDimensionsContext = createContext();

function WindowDimensionsProvider({ children }) {
  const [windowDimensions, setWindowDimensions] = useState({
    width: window.innerWidth,
    height: window.innerHeight,
  });

  useEffect(() => {
    const handleResize = () => {
      setWindowDimensions({
        width: window.innerWidth,
        height: window.innerHeight,
      });
    };

    window.addEventListener('resize',    handleResize);

    return () => {
      window.removeEventListener('resize', handleResize);
    };
  }, []);

  return (
    <WindowDimensionsContext.Provider value={windowDimensions}>
      {children}
    </WindowDimensionsContext.Provider>   
  );
}

function MyComponent() {
  const { height } = useContext(WindowDimensionsContext);

  return (
    <div>
      Viewport Height: {height} pixels
    </div>
  );
}