I'm working with controlled input elements at work and I'm stuck.
Basically, I need to autofill some input elements in a form, but the problem is that I need to fill it in a way that simulates the user input (in this case, typing) in order to trigger the onChange function's logic. So, because of that. I need to emulate the typing behavior and not just set the value for the element.
Despite having searched for previous questions and reading docs about KeyboardEvent, I haven't been able to make this work.
Currently, I'm experimenting in a Codesandbox just for making things easier, but even with this simple environment, I can't manage to get this to work.
Here's the code and its Codesandbox link
import { useRef, useState, useEffect } from "react";
import "./styles.css";
export default function App() {
const [state, setState] = useState();
const inputRef = useRef();
const event = new KeyboardEvent("keypress", { key: 99 });
useEffect(() => {
inputRef.current.dispatchEvent(event);
}, [inputRef]);
const onChange = (e) => {
setState(e.target.value);
};
return (
<div className="App">
<h1>{state}</h1>
<input
type="text"
id="name"
onChange={onChange}
ref={inputRef}
value={state}
/>
</div>
);
}
Hopefully one of you guys could give me a hand with this.
Thanks for reading!
I couldn't fix the problem with Keyboard Event for my lack of knowledge about it, but I hope I managed to solve the problem of emulating a human autofill the input using the below code.
function AutoFillInput({ finalValue }: { finalValue: string }) {
const [inputValue, setInputValue] = useState('');
const [sliceStart, setSliceStart] = useState(0);
const changeHandler = useCallback((event) => {
setInputValue(event.target.value);
}, []);
useEffect(function handleFinalValueChange() {
setInputValue('');
if (sliceStart < finalValue.length)
setSliceStart(x => x + 1);
}, [finalValue]);
useEffect(function handleSlice() {
setInputValue(finalValue.slice(0, sliceStart));
if (sliceStart < finalValue.length) {
setTimeout(() => {
setSliceStart(x => x + 1);
}, 800);
}
}, [sliceStart]);
return (
<input
value={inputValue}
onChange={changeHandler}
placeholder={'Auto fill input'}
/>
)
}
function App() {
return (
<div >
<AutoFillInput finalValue={'hello world'} />
</div>
);
}
export default App;
Related to the comments:
I think that it shouldn't be necessary to be dispatching a keypress event to get your special effect logic to run.
For example, you can use a useEffect which just runs on initial render to trigger whatever special logic you want -- and this way you can just have a regular initial value for the form state.
import { useState, useEffect } from "react";
import "./styles.css";
export default function App() {
// In the useState call, you can initialize the value.
const [state, setState] = useState("initial value");
const specialEffectFunction = () => {
// here's the code for the special effect you want to run on load
console.log('this is the special onChange effect')
}
useEffect(() => {
// This will trigger the special function which you want to run
// when the app loads
specialEffectFunction();
// if it really HAS to be the `onChange` function that's called,
// then you'll need to call that with a fake ChangeEvent.. but I don't
// think that should be necessary...
}, [])
const onChange = (e) => {
setState(e.target.value);
};
return (
<div className="App">
<h1>{state}</h1>
<input
type="text"
id="name"
onChange={onChange}
value={state}
/>
</div>
);
}