I'm using a range input in my React application. I would like to log the value selected once the range slider has changed (not while it is changing). Here is an example of my issue:
const App = () => {
const handleChange = (e) => {
console.log(e.target.valueAsNumber);
}
return <input type="range" onChange={handleChange}/>
}
ReactDOM.render(<App />, document.body);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/17.0.0/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/17.0.0/umd/react-dom.production.min.js"></script>
If you view the browser console, the value is being logged as you slide the range slider. My desired output is so that the handleChange callback is only fired once you release the slider. I would like it to behave in a similar way that onChange behaves in vanilla HTML:
const handleChange = (e) => {
console.log(e.target.valueAsNumber);
}
<input type="range" onChange="handleChange(event)"/>
It seems like react has made onChange behave like onInput, which in my case is undesirable. Is there a simple prop that I'm missing to make this work? Or do I need to use refs or some other method to make this work as intentded?
The behaviour you want is of onchange event listener. Unfortunately, React connects onChange prop to oninput event handler.
There's also an active issue about this: https://github.com/facebook/react/issues/3964 Document how React's onChange relates to onInput #3964
Simple fix would be to use onchange event listener using ref.
const NewInput = (props) => {
const setRef = useCallback((e) => {
e.target.onchange = props.onChange || null;
}, [props.onChange]);
return <input ref={setRef} {...props} />
}
Another approach is discussed here: In React, what's the difference between onChange and onInput?
Related
TL/DR: My simple toggle function fires twice when button is clicked.
I'm using useEffect in a React (w/ Next.js) component so that I can target the :root <html> tag for which I need the class to be toggled. The code is the following:
useEffect(() => {
const toggleMode = () => {
const root = document.documentElement;
root.classList.toggle("dark");
console.log("click");
};
const toggleBtn = document.querySelector("#toggle-btn");
toggleBtn.addEventListener("click", toggleMode);
I have the necessary imports, the code is placed inside the main component function before the return, and there's no errors in the console at all.
The only issue is that the function is fired twice every time the button is clicked and I cannot find any reason why or solutions online.
Would really appreciate your help and please let me know if I'm missing any information.
Cheers!
Your problem is coming from registering the event listener in a non-react way.
By registering the listener via
const toggleBtn = document.querySelector("#toggle-btn");
toggleBtn.addEventListener("click", toggleMode);
you are setting up a new listener each time the function is run, even if the DOM is not updated. This could result in multiple listeners being registered and firing simultaneously.
You need to add your listener the react way.
function Component ( props ){
const [ isFirst, setIsFirst ] = useState( true );
const [ toggle, setToggle ] = useState( false );
useEffect(() => {
if( isFirst ) {
setIsFirst( false );
return;
}
document.documentElement.classList.toggle("dark");
}, [ toggle ] );
return <div>
<button id="toggle-btn" onClick = { e => setToggle( !toggle ) } />
</div>
}
I resolved a similar problem in this post: Why does my NextJS Code run multiple times, and how can this be avoided?
Your code should only run once if you disable react strict mode.
I am adding an event listener and checking if its level 1, but when I press the space key once, it fires 50times or more. Please help
document.addEventListener("keyup", function(e) {
if(level === 1){
if(e.code === "Space") {
console.log('space press');
click1();
}
}
});
Since this is tagged with React, given the code you have here and the issue you describe, it is almost certain that you are binding an event listener every render. Which means you are ending up with way more listeners than you want. What you need to do is use React when you are using React.
For example below, we have an input that logs on any keypress, and we also manually create an event listener. At first, when you type, you will get one log for each. However, once you click the button (triggering a rerender), you will start getting multiple "manual" events, but still the single "react" event:
class Hello extends React.Component {
constructor(props) {
super(props);
this.state = { count: props.count };
}
inc() {
this.setState(prev => ({count: prev.count+1}));
}
render() {
document.addEventListener("keyup", function(e) {
console.log('manual space press');
});
return <div onKeyUp={(e) => {
console.log('React: space press');
}}>
<button onClick={() => this.inc()}>{this.state.count}</button>
<input />
</div>
}
}
ReactDOM.render(<Hello count={0}/>, 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'></div>
This is something called Event Bubblingwhich basically means that the event gets fired once on each parent element until it reached HTML.
you can learn about it here: https://dev.to/eladtzemach/event-capturing-and-bubbling-in-react-2ffg#:~:text=Event%20Bubbling%20and%20Capturing%20in%20React&text=Bubbling%20is%20as%20straightforward%20as,our%20example%20in%20the%20beginning.
you are able to prevent the default behavior but it's generally a good practice to leave it as is if you don't have a specific use for disabling it.
from the code snippet, I don't see why is this tagged with react but another reason for your problem is that you may be putting this code inside of your render() function or inside of any react life cycle function which is causing this snippet to run with each rerender leaving you with a punch of unwanted listeners which is not only functionality you don't want but also something that will slow down you app
overtime ie. until the user refresh the page.
useEffect(() => {
const handleEscape = (event) => {
if (event.keyCode === 27) {
console.log('Hello')
}
};
window.addEventListener('keydown', handleEscape);
return () => {
window.removeEventListener('keydown', handleEscape);
};
}, []);
What I want to do is have an input that a user can type into. Upon clicking a button, take that input and process it and perform some backend operations with the database connected to the input. I'm trying to accomplish this with a state hook: onBlur, save input into state. On button click, do two things: 1) take the state variable and pass it to the backend resolvers, and 2) clear the input field so it's empty, and only the placeholder text exists.
I have this code:
const [inputVal, setInputVal] = useState("");
updateInput = (e) => {
const val = e.target.value;
setInputVal(val);
}
sendData = async () => {
//handle async backend processing with inputVal
setInputVal("");
//rerender
}
<Button className="input-button" onClick={sendData}>Send Data</Button>
<input className="input-field" placeHolder="Input name." defaultValue={inputVal} onBlur=(updateInput)></input>
However, I have two issues.
On button click, I want to first updateInput, and then handle the button click, so it always uses the new value. However, it seems as if there are some issues with that, possibly due to the asynchronous nature of sendData?
While inputVal may be an empty String, for some reason, the value in the input box doesn't reset to nothing, it stays exactly as it was (although the internal data would still have inputVal = 0). And onBlur it reupdates the inputVal.
for a controlled state input the most common approach is to use onChange rather than onBlur. This would also avoid your conflicts with blur and click events. Also you would pass inputVal to value input's property.
const [inputVal, setInputVal] = useState("");
const updateInput = (e) => {
const val = e.target.value;
setInputVal(val);
}
const sendData = async () => {
//handle async backend processing with inputVal
setInputVal("");
//rerender
}
return (
<>
<button className="input-button" onClick={sendData}>Send Data</button>
<input className="input-field" onChange={updateInput} placeHolder="Input name." value={inputVal}/>
</>
);
First, change defaultValue to value={inputVal} since it's a controlled input.
Secondly, please elaborate on what issues you have in 1.
I have the following code where I am only enabling a button if relevant data exists.
I am trying to test this by faking a change in the input field so that the relevant data is available.
But my simulation does not seem to work thus the data remains empty which in turn means my button remains disabled. Can I please get some help on what I am doing wrong please? Thank you.
Note that following code works where events fires as expected and updates. Just issue in writing test.
const [code1, setCode1] = useState('');
const cannotPress = () => !(code1);
const handleFieldChange = (event, updater) => {
updater(event.target.value);
};
// in test, trying to simulate a value entered in this input so that the event fires and
// updates code1's value thus making cannotPress=false. This would enable the button and pass test.
<input id="code1" value={code1} onChange={event => handleFieldChange(event, setCode1)} />
<button id='btn type="submit" disabled={cannotPress()} onClick={() => doSomething()}>Submit</button>
Test
describe('tests', () => {
const wrapper = shallow(<MyApp info={info} />);
it('simple test', () => {
const btn = wrapper.find('button#btn'); // able to find button
const input = wrapper.find('input#code1'); // able to find input (tested by placing in default values)
console.log(input.props().value); // prints nothing as expected
input.instance().props.onChange(({ target: { value: 'some fake data' } })); // expecting the event to trigger and change value for code1.
console.log(input.props().value); // ISSUE: expected to print 'some fake data' but still empty.
expect(btn.prop('disabled')).toBe(false); // fails cos input has no value thus disabled is still true
});
});
I think you will need to simulate the event (using enzyme) rather then trying to manipulate the onChange() property directly.
Seems like a similar issue to:
https://stackoverflow.com/a/37452043/10610784
Try the suggested solution
input.simulate('change', { target: { value: 'Hello' } })
The bounty expires in 7 days. Answers to this question are eligible for a +50 reputation bounty.
ajaykools wants to reward an existing answer:
Worth bounty, only way simulate clicks on dynamic elements like svg, g, circle, etc which are generated on page load.
I'm trying to simulate a .click() event on a React element but I can't figure out why it is not working (It's not reacting when I'm firing the event).
I would like to post a Facebook comment using only JavaScript but I'm stuck at the first step (do a .click() on div[class="UFIInputContainer"] element).
My code is:
document.querySelector('div[class="UFIInputContainer"]').click();
And here's the URL where I'm trying to do it: https://www.facebook.com/plugins/feedback.php...
P.S. I'm not experienced with React and I don't know really if this is technically possible. It's possible?
EDIT: I'm trying to do this from Chrome DevTools Console.
React tracks the mousedown and mouseup events for detecting mouse clicks, instead of the click event like most everything else. So instead of calling the click method directly or dispatching the click event, you have to dispatch the down and up events. For good measure I'm also sending the click event but I think that's unnecessary for React:
const mouseClickEvents = ['mousedown', 'click', 'mouseup'];
function simulateMouseClick(element){
mouseClickEvents.forEach(mouseEventType =>
element.dispatchEvent(
new MouseEvent(mouseEventType, {
view: window,
bubbles: true,
cancelable: true,
buttons: 1
})
)
);
}
var element = document.querySelector('div[class="UFIInputContainer"]');
simulateMouseClick(element);
This answer was inspired by Selenium Webdriver code.
With react 16.8 I would do it like this :
const Example = () => {
const inputRef = React.useRef(null)
return (
<div ref={inputRef} onClick={()=> console.log('clicked')}>
hello
</div>
)
}
And simply call
inputRef.current.click()
Use refs to get the element in the callback function and trigger a click using click() function.
class Example extends React.Component{
simulateClick(e) {
e.click()
}
render(){
return <div className="UFIInputContainer"
ref={this.simulateClick} onClick={()=> console.log('clicked')}>
hello
</div>
}
}
ReactDOM.render(<Example/>, document.getElementById('app'))
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="app"></div>
If you don't define a class in your component, and instead you only declare:
function App() { ... }
In this case you only need to set up the useRef hook and use it to point/refer to any html element and then use the reference to trigger regular dom-events.
import React, { useRef } from 'react';
function App() {
const inputNameRef = useRef()
const buttonNameRef = useRef()
function handleKeyDown(event) {
// This function runs when typing within the input text,
// but will advance as desired only when Enter is pressed
if (event.key === 'Enter') {
// Here's exactly how you reference the button and trigger click() event,
// using ref "buttonNameRef", even manipulate innerHTML attribute
// (see the use of "current" property)
buttonNameRef.current.click()
buttonNameRef.current.innerHTML = ">>> I was forced to click!!"
}
}
function handleButtonClick() {
console.log('button click event triggered')
}
return (
<div>
<input ref={inputNameRef} type="text" onKeyDown={handleKeyDown} autoFocus />
<button ref={buttonNameRef} onClick={handleButtonClick}>
Click me</button>
</div>
)
}
export default App;
A slight adjustment to #carlin.scott's great answer which simulates a mousedown, mouseup and click, just as happens during a real mouse click (otherwise React doesn't detect it).
This answer adds a slight pause between the mousedown and mouseup events for extra realism, and puts the events in the correct order (click fires last). The pause makes it asynchronous, which may be undesirable (hence why I didn't just suggest an edit to #carlin.scott's answer).
async function simulateMouseClick(el) {
let opts = {view: window, bubbles: true, cancelable: true, buttons: 1};
el.dispatchEvent(new MouseEvent("mousedown", opts));
await new Promise(r => setTimeout(r, 50));
el.dispatchEvent(new MouseEvent("mouseup", opts));
el.dispatchEvent(new MouseEvent("click", opts));
}
Usage example:
let btn = document.querySelector("div[aria-label=start]");
await simulateMouseClick(btn);
console.log("The button has been clicked.");
Note that it may require page focus to work, so executing in console might not work unless you open the Rendering tab of Chrome DevTools and check the box to "emulate page focus while DevTools is open".
Inspired from previous solution and using some javascript code injection it is also possibile to first inject React into the page, and then to fire a click event on that page elements.
let injc=(src,cbk) => { let script = document.createElement('script');script.src = src;document.getElementsByTagName('head')[0].appendChild(script);script.onload=()=>cbk() }
injc("https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js",() => injc("https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js",() => {
class ReactInjected extends React.Component{
simulateClick(e) {
e.click()
}
render(){
return <div className="UFIInputContainer"
ref={this.simulateClick} onClick={()=> console.log('click injection')}>
hello
</div>
}
}
ReactDOM.render(<ReactInjected/>, document.getElementById('app'))
} ))
<div id="app"></div>
Kind of a dirty hack, but this one works well for me whereas previous suggestions from this post have failed. You'd have to find the element that has the onClick defined on it in the source code (I had to run the website on mobile mode for that). That element would have a __reactEventHandlerXXXXXXX prop allowing you to access the react events.
let elem = document.querySelector('YOUR SELECTOR');
//Grab mouseEvent by firing "click" which wouldn't work, but will give the event
let event;
likeBtn.onclick = e => {
event = Object.assign({}, e);
event.isTrusted = true; //This is key - React will terminate the event if !isTrusted
};
elem.click();
setTimeout(() => {
for (key in elem) {
if (key.startsWith("__reactEventHandlers")) {
elem[key].onClick(event);
}
}
}, 1000);
Using React useRef Hooks you can trigger a click event on any button like this:
export default const () => {
// Defining the ref constant variable
const inputRef = React.useRef(null);
// example use
const keyboardEvent = () => {
inputRef.current.handleClick(); //Trigger click
}
// registering the ref
return (
<div ref={inputRef} onClick={()=> console.log('clicked')}>
hello
</div>
)
}
This answer was inspired by carlin.scott code.
However, it works only with focusin event in my case.
const element = document.querySelector('element')
const events = ['mousedown', 'focusin']
events.forEach(eventType =>
element.dispatchEvent(
new MouseEvent(eventType, { bubbles: true })
)
)