Suppose there's the following simple component. When I click on the button, the message will change to Clicked for 1 second and then goes back to -. However, when I spam the button, I want the title to be Clicked but it should go back to - after the last click of the button. Basically, I want each click to expand the timeout.
If this was a simple JS function, I would just clear the interval after each click and set another timeout. However, I'm not sure how to achieve the same result using react hooks.
import ReactDOM from 'react-dom';
import {useEffect, useState} from 'react';
import './index.css';
const Test = () => {
const [message, setMessage] = useState("-");
const buttonClick = () => {
setMessage("Clicked");
}
useEffect(() => {
if(message !== "-") {
const id = setTimeout(() => {
console.log("Running Interval");
setMessage("-");
}, 1000);
return () => {
console.log("Clearing Interval");
clearTimeout(id);
}
}
}, [message]);
return (
<article>
<header>
{message}
</header>
<button onClick={buttonClick}>button</button>
</article>
);
}
Put the timeout ID into a ref, and then you can call clearTimeout on it at the very beginning of the click handler.
const Test = () => {
const [message, setMessage] = React.useState("-");
const timeoutIdRef = React.useRef();
const handleClick = () => {
setMessage("Clicked");
clearTimeout(timeoutIdRef.current);
timeoutIdRef.current = setTimeout(() => {
setMessage("-");
}, 1000);
};
// cleanup, if desired
// React.useEffect(() => clearTimeout(timeoutIdRef.current), []);
return (
<article>
<header>
{message}
</header>
<button onClick={handleClick}>button</button>
</article>
);
}
ReactDOM.render(<Test />, document.querySelector('.react'));
<script crossorigin src="https://unpkg.com/react#16/umd/react.development.js"></script>
<script crossorigin src="https://unpkg.com/react-dom#16/umd/react-dom.development.js"></script>
<div class='react'></div>
Related
I have found this error while trying to build another React app. So I am only asking the main issue here in a demo app, I might not be able to change any rendering methods here since it is not the actual project.
Issue in simplified form -> I was building a app where two count will be shown and a + button will be there next to that count value. When the button is clicked the count should be increased by 1. Unfortunately when I try to click on the button the value is increasing only the first time. After that the value is not even changing. But when I am implementing the same using Class component its working as expected.
Functional Component
import React, { useState } from "react";
function Page(props) {
const [count, setCount] = useState(0);
const [content, setContent] = useState({
button: (value) => {
return <button onClick={() => handlePlus(value)}>+</button>;
},
});
function handlePlus(value) {
console.log("value=", value);
const data = count + 1;
setCount((count) => data);
}
return (
<div>
<span>Functional Component Count = {count}</span>
{content.button(10)} // 10 will be replaced with another variable
</div>
);
}
export default Page;
Class Component
import React, { Component } from "react";
class PageClass extends Component {
state = {
count: 0,
content: {
button: (value) => {
return (
<button onClick={() => this.handlePlus(value)}>+</button>
);
},
},
};
handlePlus = (value) => {
console.log("value=", value);
this.setState({ count: this.state.count + 1 });
};
render() {
return (
<div>
<span>Class Component Count = {this.state.count}</span>
{this.state.content.button(10)} // 10 will be replaced with another variable
</div>
);
}
}
export default PageClass;
App.js
import "./App.css";
import Page from "./components/Page";
import PageClass from "./components/PageClass";
function App() {
return (
<div className="App">
<Page />
<PageClass />
</div>
);
}
export default App;
However, If I replace that content state variable with normal const variable type and it is working as expected.
Below is working when I am not using any hooks to render the button.
But this is not helpful for my case.
const content = {
content: () => {
console.log(count);
return <button onClick={() => handlePlus(value)}>+</button>;
},
};
I was trying to create some re-usable components and hence I wanted to have that function in state variable which return button tag, so that I can implements some other logic there.
The value will be missing since you're passing a hard-coded 10.
I'd recommend simplifying the handlePlus to just:
setCount(c => c + 1);
Then set the onclick like so:
<button onClick={handlePlus}>+</button>
And your code will work as expected as you can see in this snippet:
const { useState } = React;
const Example = () => {
const [count, setCount] = useState(0);
const [content, setContent] = useState({
content: (value) => {
return <button onClick={handlePlus}>+</button>;
},
});
function handlePlus(value) {
setCount(c => c + 1);
}
return (
<div>
<span>{count}</span>
{content.content(10)}
</div>
);
}
ReactDOM.render(<Example />, document.getElementById("react"));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/17.0.1/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/17.0.1/umd/react-dom.production.min.js"></script>
<div id="react"></div>
That said, I'd recommend removing the button from the hook, and just render it yourself:
const { useState } = React;
const Example = () => {
const [count, setCount] = useState(0);
function handlePlus(value) {
setCount(c => c + 1);
}
return (
<div>
<span>{count}</span>
<button onClick={handlePlus}>+</button>
</div>
);
}
ReactDOM.render(<Example />, document.getElementById("react"));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/17.0.1/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/17.0.1/umd/react-dom.production.min.js"></script>
<div id="react"></div>
See React documentation about the c => c + 1 syntax
I have this useEffect function in react component. I am calling api videoGridState here.
Now what is happening here it is calling my api 2 times one at intitial page reaload and second one when count is changing. I want it to be called single time when page reloads. But also when streamSearchText changes
const [count, setCount] = useState(0);
const [streamSearchText, setStreamSearchText] = useState("");
useEffect(() => {
videoGridState();
}, [count]);
useEffect(() => {
const delayDebounceFn = setTimeout(() => {
setCount(count + 1);
}, 1000);
return () => clearTimeout(delayDebounceFn);
}, [streamSearchText]);
How can I do that?
The main issue is that you have two useEffect calls, and so they're each handled, and the second triggers the first (after a delay), resulting in the duplication.
As I understand it, your goal is:
Run videoGridState immediately on mount, and
Run it again after a delay of 1000ms whenever streamSearchText changes
That turns out to be surprisingly awkward to do. I'd probably end up using a ref for it:
const firstRef = useRef(true);
const [streamSearchText, setStreamSearchText] = useState("");
useEffect(() => {
if (firstRef.current) {
// Mount
videoGridState();
firstRef.current = false;
} else {
// `streamSearchText` change
const timer = setTimeout(() => {
videoGridState();
}, 1000);
return () => clearTimeout(timer);
}
}, [streamSearchText]);
Live Example:
const { useState, useRef, useEffect } = React;
function videoGridState() {
console.log("videoGridState ran");
}
const Example = () => {
const firstRef = useRef(true);
const [streamSearchText, setStreamSearchText] = useState("");
useEffect(() => {
if (firstRef.current) {
// Mount
videoGridState();
firstRef.current = false;
} else {
// `streamSearchText` change
const timer = setTimeout(() => {
videoGridState();
}, 1000);
return () => clearTimeout(timer);
}
}, [streamSearchText]);
return <div>
<label>
Search text:{" "}
<input
type="text"
value={streamSearchText}
onChange={(e) => setStreamSearchText(e.currentTarget.value)}
/>
</label>
</div>;
};
const root = ReactDOM.createRoot(document.getElementById("root"));
root.render(<Example />);
<div id="root"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/18.1.0/umd/react.development.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/18.1.0/umd/react-dom.development.js"></script>
You could also do the query immediately when streamSearchText is "", but that would happen every time streamSearchText was "", not just on mount. That may be good enough, depending on how rigorous you need to be.
Additionally, though, if you're still seeing something happen "on mount" twice, you may be running a development copy of the libraries with React.StrictMode around your app (the default in many scaffolding systems). See this question's answers for details on how React.StrictMode may mount your component more than once and throw in other seeming surprises.
Your following useEffect() function makes this behaviour to happen:
useEffect(() => {
const delayDebounceFn = setTimeout(() => {
setCount(count + 1);
}, 1000);
return () => clearTimeout(delayDebounceFn);
}, [streamSearchText]);
Since it runs initially but called setCount() which updates the state, and forces a re-render of the component which in turn runs the first useEffect() since that has [count] in the dependency array.
And hence the cycle continues for the [count]
const Example = () => {
const { useState, useRef, useEffect } = React;
// Any async function or function that returns a promise
function myDownloadAsyncFunction(data) {
console.log("222222222222222222222")
return new Promise((resolve) => setTimeout(resolve, 1000));
}
function DownloadButton() {
const [queue, setQueue] = useState(Promise.resolve());
onClickDownload = () => {
setQueue(queue
.then(() => myDownloadAsyncFunction('My data'))
.catch((err) => {console.error(err)})
)
}
return (
<button onClick={onClickDownload()}>Download</button>
);
}
}
const root = ReactDOM.createRoot(document.getElementById("root"));
root.render(<Example />);
<div id="root"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/18.1.0/umd/react.development.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/18.1.0/umd/react-dom.development.js"></script>
I have a component that after a user has clicked the button, a message appears and should disappear after 3 seconds. I'm trying to use useEffect to enable the timeout, but can't get it working:
const { useState, useEffect } = React
const SectionHeader = (props) => {
const {title, button, link, type} = props;
const [copy, setCopy] = useState(false)
const [showMessage, setShowMessage] = useState(true);
useEffect(() => {
setTimeout(() => {
setShowMessage(false)
}, 3000)
}, [])
const copyToClipboard = (title) => {
navigator.clipboard.writeText(window.location.href + '#' + title.toLowerCase().replaceAll(" ", "-").replaceAll("'", ""))
setCopy(true)
}
return (
<div id={title.toLowerCase().replaceAll(" ", "-").replaceAll("'", "")}>
<b>{title}</b>
<div onClick={() => copyToClipboard(title)}>Copy to clipboard</div> {copy ? 'copied' : ''}
</div>
)
}
ReactDOM.render(<SectionHeader title="Test" />,
document.getElementById("root"))
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="root">
useEffect execute the code written in its block only when the website is loaded for the first time or when the dependencies changes.
In your code you have not included any dependencies, so it'll only execute the code wrapped inside its block when the site will load for the first time.
useEffect(() => {
setTimeout(() => {
setShowMessage(false)
}, 3000)
}, [here should be some state which changes when a button got clicked])
In my code below, how to call executeBeforeToggle function before executing parent's function togglePage?
import * as React from "react";
import { useState } from "react";
import { render } from "react-dom";
const Page1 = (props) => {
//how to call this function before toggling?
const executeBeforeToggle = () => {
alert('HOORAY')
}
return (
<div>
<h1>I am Page 1</h1>
<button onClick={() => props.togglePage()}>Toggle</button>
</div>
)
};
const Page2 = (props) => {
return (
<div>
<h1>I am Page 2</h1>
<button onClick={() => props.togglePage()}>Toggle</button>
</div>
)
}
const App = () => {
const [page, setPage] = useState(false)
const togglePage = () => {
setPage(!page)
}
if(page === false) return <Page1 togglePage={togglePage} />
else return <Page2 togglePage={togglePage} />
}
render(<App />, document.getElementById("root"));
Not sure if I understood your question correctly, but actually that is simple:
const Page1 = (props) => {
const executeBeforeToggle = () => {
alert('HOORAY')
}
const handleClick = () => { // click handler which exec both funcs
executeBeforeToggle();
props.togglePage();
}
return (
<div>
<h1>I am Page 1</h1>
<button onClick={handleClick}>Toggle</button>
</div>
)
};
So the main idea is that your click handler should be a function which executes both executeBefore and togglePage functions in the order you need. You may write that right inside the buttons onClick, or (as above) create separate function and pass it into the onClick what makes code a bit more readable.
I am creating a stopwatch in React.js and i am wondering why window.addEventListener('keydown', callback) re-render my component?
import { useEffect, useState } from 'react';
import './App.scss';
import Timer from './Timer';
import Button from './Button';
import Time from './Time';
const App = () => {
const [isRunning, setIsRunning] = useState(false);
const [start, setStart] = useState(new Time(0));
const [stop, setStop] = useState(new Time(0));
const handleStart = () => {
const now = new Date();
setIsRunning(true);
setStart(new Time(now));
setStop(new Time(now));
};
const handleStop = () => {
setIsRunning(false);
setStop(new Time(new Date()));
};
const getTime = () => {
if (isRunning) {
return new Time(new Date().getTime() - start.origin);
} else {
return new Time(stop.origin - start.origin);
}
};
const handleKeyDown = (key) => {
console.log(key.code === 'Space');
};
useEffect(() => {
window.addEventListener('keydown', handleKeyDown);
return () => {
window.removeEventListener('keydown', handleKeyDown);
};
});
return (
<div className="stopwatch">
<Timer getTime={getTime} />
<div className="buttons">
<Button role={'start'} callback={handleStart} />
<Button role={'stop'} callback={handleStop} />
</div>
</div>
);
};
export default App;
When i click start and then stop after let's say 3s. <Timer /> show correctly time that has passed, but then when i press Space on keyboard <Timer /> is re-rendering, showing new time. Then, when i switch my web-browser to VSCode and again to web-browser, <Timer /> isn't re-rendering
Here is my Timer component
import { memo, useEffect, useRef } from 'react';
const Timer = ({ getTime }) => {
const timer = useRef();
console.log('timer rendered');
useEffect(() => {
function run() {
const time = getTime().formatted();
timer.current.textContent = `${time.m}:${time.s}.${time.ms}`;
requestAnimationFrame(run);
}
run();
return () => {
cancelAnimationFrame(run);
};
});
return <div ref={timer} className="timer"></div>;
};
export default memo(Timer);
no matter if I use [] in both or none of useEffect nothing changes.
As #davood-falahati says, adding an empty array as a second argument to useEffect would probably be desirable. From the docs:
... If you want to run an effect and clean it up only once (on mount and unmount), you can pass an empty array ([]) as a second argument. This tells React that your effect doesn’t depend on any values from props or state, so it never needs to re-run. This isn’t handled as a special case — it follows directly from how the dependencies array always works. ...
In your use case:
useEffect(() => {
window.addEventListener('keydown', handleKeyDown);
return () => {
window.removeEventListener('keydown', handleKeyDown);
};
}, []);