usePageBottom hook
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Detect if the user scrolled to the bottom of the page
React Hooks Handbook
1
Intro to React Hooks
3:39
2
Create your first React app
4:23
3
React Component
2:54
4
Styling in React
5:06
5
Styles and Props
2:22
6
Understanding Hooks
3:21
7
useState Hook
2:54
8
useEffect Hook
3:41
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useRef Hook
3:00
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Props
3:11
11
Conditional Rendering
4:21
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Load Local Data
4:04
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Fetch Data from an API
5:40
14
Toggle a state
4:05
15
useInput Hook
6:04
16
Gatsby and React
6:44
17
NextJS and React
5:24
18
React TypeScript Part 1
8:19
19
React TypeScript Part 2
7:35
20
useScrollPosition Hook
4:26
21
useOnScreen hook
8:08
22
useContext Hook
8:32
23
Fragments
2:43
24
Lazy Loading
4:05
25
React Suspense
3:13
26
Environment Variables
4:43
27
Reach Router
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28
URL Params
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29
SEO and Metadata
6:47
30
Favicon
3:03
31
Dynamic Favicon
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32
PropTypes
3:54
33
Custom PropTypes
3:58
34
useMemo Hook
4:05
35
forwardRef Hook
3:28
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Handling Events
5:44
37
Spread attributes
3:35
38
useMousePosition Hook
4:55
39
useReducer with useContext Part 1
7:33
40
useReducer with useContext Part 2
6:48
41
useReducer with useContext Part 3
5:43
42
Netlify
5:08
43
Gatsby Cloud
6:19
44
Gatsby Plugin Image
8:11
45
useOnClickOutside Hook
6:32
46
useWindowSize Hook
4:14
47
usePageBottom hook
4:48
48
useLocalStorage Hook
5:27
49
Three.js in React Part 1
17:33
50
Three.js in React Part 2
11:18
CodeSandbox link
You can find the full code for this tutorial, with styling, at https://codesandbox.io/s/usepagebottom-hook-v67jq.
Create the hook
In a new usePageBottom.js file, import useState and useEffect from the React library.
// src/usePageBottom.js
import { useState, useEffect } from 'react';Define the usePageBottom hook. Don't forget to export default the hook at the bottom.
// src/usePageBottom.js
const usePageBottom = () => {}
export default usePageBottomInside of the hook, define a reachedBottom state, and set it by default to false.
// src/usePageBottom.js
const [reachedBottom, setReachedBottom] = useState(false);Let's defined the useEffect inside of the hook.
useEffect(() => {}, []);Next, we'll add a function called handleScroll inside of the useEffect . This will be called when we'll listen to the scroll event.
// src/usePageBottom.js
useEffect(() => {
const handleScroll = () => {
const offsetHeight = document.documentElement.offsetHeight;
const innerHeight = window.innerHeight;
const scrollTop = document.documentElement.scrollTop;
const hasReachedBottom = offsetHeight - (innerHeight + scrollTop) <= 10;
setReachedBottom(hasReachedBottom);
};
}, []);In the handleScroll above, we're getting three values: the offsetHeight of the document, the innerHeight of the window and the scrollTop of the document. The offsetHeight is the height of the element. The innerHeight of the window is the height of the window. The scrollTop calculates the distance the user scrolled from the top of the document, to their current position, if the element is scrollable. Finally, we're calculating if the user has reached the bottom by calculating if they're at least 10 pixels from the bottom of the page, and saving it in a hasReachedBottom variable. We're then setting the reachedBottom state with the hasReachedBottom variable. Right below the handleScroll function, we'll add an event listener to the window . We'll listen to the scroll event, and when that event is fired, we'll call the handleScroll function.
// src/usePageBottom.js
useEffect(() => {
const handleScroll = () => {
const offsetHeight = document.documentElement.offsetHeight;
const innerHeight = window.innerHeight;
const scrollTop = document.documentElement.scrollTop;
const hasReachedBottom = offsetHeight - (innerHeight + scrollTop) <= 10;
setReachedBottom(hasReachedBottom);
};
window.addEventListener("scroll", handleScroll);
}, []);The last line of the useEffect is the cleanup function. We'll remove the event listener there.
useEffect(() => {
const handleScroll = () => {
const offsetHeight = document.documentElement.offsetHeight;
const innerHeight = window.innerHeight;
const scrollTop = document.documentElement.scrollTop;
const hasReachedBottom = offsetHeight - (innerHeight + scrollTop) <= 10;
setReachedBottom(hasReachedBottom);
};
window.addEventListener("scroll", handleScroll);
return () => window.removeEventListener("scroll", handleScroll);
}, []);At the bottom of the usePageBottom hook, we'll return the reachedBottom state.
// src/usePageBottom.js
const usePageBottom = () => {
const [reachedBottom, setReachedBottom] = useState(false);
// useEffect here...
return reachedBottom
};Find below the final code for the usePageBottom hook.
// src/usePageBottom.js, final code
import { useState, useEffect } from "react";
const usePageBottom = () => {
const [reachedBottom, setReachedBottom] = useState(false);
useEffect(() => {
const handleScroll = () => {
const offsetHeight = document.documentElement.offsetHeight;
const innerHeight = window.innerHeight;
const scrollTop = document.documentElement.scrollTop;
const hasReachedBottom = offsetHeight - (innerHeight + scrollTop) <= 10;
setReachedBottom(hasReachedBottom);
};
window.addEventListener("scroll", handleScroll);
return () => window.removeEventListener("scroll", handleScroll);
}, []);
return reachedBottom
};
export default usePageBottom;Use the hook
Now, it's time the use the hook. First, let's create our page, and add some height to it.
// src/MyPage.js
import styled from "styled-components";
const MyPage = () => {
return <Wrapper>Hello world!</Wrapper>;
};
export default MyPage;
const Wrapper = styled.div`
height: 200vh;
padding: 20px;
background: rgba(0, 0, 0, 0.2);
`;Now, let's import the hook.
// src/MyPage.js
import usePageBottom from "./usePageBottom";And let's call the hook! Now, when the user has reached at last 10px from the bottom of the page, the reachedBottom value printed on the console will be true . Otherwise, it'll be false.
const reachedBottom = usePageBottom();
console.log("reachedBottom", reachedBottom);Learn with videos and source files. Available to Pro subscribers only.
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usePageBottom hook
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useLocalStorage Hook
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Three.js in React Part 1
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