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how to validate user inputs in react using setState hook

I have a form. In the form I getting brandName, supplierName, and date of expiry from the user.
I am usinf TextField from mui library and submit button.
I want to disable submit button on empty form fields and enable it when user filled all the inputs
here is my code for declaring useStates
const[brandName, setBrandName] = useState("");
const[supplierName, setSupplierName] = useState("");
const[expiryDate, setExpiryDate] = useState(null);
const[brandNameError, setBrandNameError] = useState(false);
const[supplierNameError, setSupplierNameError] = useState(false);
const[expiryDateError, setExpiryDateError] = useState(false);
const[submitButton, setSubmitButton] = useState(true);
and here is all function which i used to validate my inputs
// checking brandName Error
const brandNameValidateOnBlur = ()=>{
if(brandName === ""){
setBrandNameError(true);
}
}
// checking supplier name error
const supplierNameValidateOnBlur = ()=>{
if(supplierName === ""){
setSupplierNameError(true);
}
}
// checking expiry date
const expiryDateValidateOnBlur = ()=>{
if(expiryDate === ""){
setExpiryDateError(true);
}
}
// now checking all inputs again if all inputs are good then
// button should be enabled
const checkAllInputs = ()=>{
if(brandName !== "" && supplierName !== "" && expiryDate !== ""){
setSubmitButton(false);
}else{
setSubmitButton(true);
}
}
and here is the rest of code
<TextField fullWidth id="productName" label="Product Name"
value={brandName.toLowerCase()} variant="outlined"
onChange={(data)=>{setBrandName(data.target.value.toUpperCase());checkAllInputs()}}
onBlur={brandNameValidateOnBlur}
onFocus={()=>setBrandNameError(false)}
error={brandNameError}
helperText = {brandNameError ? "Enter Brand Name" : ""}
/>
<TextField id="supplierName"
label="Supplier Name"
value={supplierName.toLowerCase()} variant="outlined"
onBlur={supplierNameValidateOnBlur}
onFocus={()=>setSupplierNameError(false)}
error={supplierNameError}
helperText={supplierNameError ? "Enter Supplier Name " : ""}
onChange={(data)=>{setSupplierName(data.target.value.toUpperCase());checkAllInputs()}} />
<LocalizationProvider dateAdapter={AdapterDayjs}>
<DesktopDatePicker
label="Date Expiry"
inputFormat="MM/DD/YYYY"
value={expiryDate}
onBlur={expiryDateValidateOnBlur}
onFocus={()=>setExpiryDateError(false)}
error={expiryDateError}
helperText={expiryDateError ? "Enter Expiry Date ": ""}
onChange={(selectedDate)=>
{setExpiryDate(selectedDate.format("MM/DD/YYYY"));checkAllInputs()}}
renderInput={(params) => <TextField {...params} />}
/>
</LocalizationProvider>
<Button type='button' variant='contained' id="submitButton" disabled={submitButton}
style={{backgroundColor:'orangered'}} onClick={addData}>Add Data</Button>
now problem is when i enter a single word my useState is updated but my checkAllInputs not working as i want to be like if i enter a word my checkAllInputs method runs before setting of state as i enter second entry then it works like I want to be so i did not know what i am doing wrong
I TRY useEffect hook like that
useEffect(()=>{
checkAllInputs();
},[brandName, supplierName, expiryDate]);
its working fine as i accepted but I read that it should be a expensive to use useEffect
and an other approach which i use
const checkAllInputsWithDom = ()=>{
let brandNameEntry = document.getElementById("brandName").value;
let supplierNameEntry = document.getElementById("supplierName").value;
let expiryDateEntry = document.getElementById("expiryDate").value;
if(brandNameEntry !=="" && supplierNameEntry !== "" && expiryDateEntry !== ""){
setSubmitButton(false);
}else{
setSubmitButton(true);
}
}
it is working out of box but I thing in react this is against react principles to direct manipulate
dome elements can I do it with out using useeffect hook like only with my metohd and one more thing
this did not set expiryDate error in date field

As long as you're keeping the input values in state, you don't need another variable storing the button state as well. You can calculate it at render time. (Read more about avoiding redundant state here.)
You could do something like this:
const Component = () => {
const[brandName, setBrandName] = useState("");
const[supplierName, setSupplierName] = useState("");
const[expiryDate, setExpiryDate] = useState("");
const disabled = brandName.length === 0 && supplierName.length === 0 && expiryDate.length === 0
return (
<>
<input value={brandName} onChange={(e) => setBrandName(e.target.value)}/>
<input value={supplierName} onChange={(e) => setSupplierName(e.target.value)}/>
<input value={expiryDate} onChange={(e) => setExpiryDate(e.target.value)}/>
<button disabled={disabled}>Button</button>
</>
)
}

here is the link for codesandbox I have a suggestion for you to refactor this 6 use States with just one useState as an object having all the values like the following:
const initialValues = {
brandName: "",
supplierName: "",
expiryDate: "",
brandNameError: "",
supplierNameError: "",
expiryDateError: ""
};
and then update it with a generic handleInputChange like below:
const handleInputChange = (e) => {
//const name = e.target.name
//const value = e.target.value
const { name, value } = e.target;
setValues({
...values,
[name]: value
});
let isEmpty = Object.values(values).some((x) => x === "");
console.log(isEmpty);
setIsDisabled(isEmpty);
};
FOR YOUR SOLUTION
You will have to just check all the values and just create a boolean with isDisabled so when all of those values are empty then it will only set to false.
I have created a code snippet for you, it needs some improvement but it will serve your purpose. Link already at the top and here as well

as suggested by Eduardo Motta de Moraes
I used this for making my button enabled after all inputs validate
const disabled= brandName.length === 0 || supplierName.length === 0 || expiryDate.length === 0;
this solve my problem
thanks for Eduardo Motta de Moraes for this

Toggle correct answer message with radio button in React

Given a small quiz app, I'm trying to toggle a message under the questions to show the user that they have selected the correct answer or incorrect answer.
I have a small message that I'm gating with a boolean value which is set by the selection of the radio button (though the correct radio button isn't getting selected on initial click for some reason, only incorrect answers are), and need it to show a message of "You got it right" if the answer is true or "incorrect" if false. I can show true, but the logic isn't working to show false if the answer is incorrect and then clear the messaging when the "next question" button is clicked.
function App() {
let [points, setPoints] = useState(null);
let [counter, setCounter] = useState(null);
let [question, setQuestions] = useState();
let [isCorrect, setIsCorrect] = useState(false); <==Store correct answer selected
function Answer(props) {
return (
<li aria-labelledby="answers-list">
<label>
<input
type="radio"
name="answer_group"
className="answer"
value={props.answer}
onChange={checkAnswer}
/>
{props.answer}
</label>
</li>
);
}
function checkAnswer(e) {
let val = e.target.value;
let ans = question[counter].answers.filter((ans) => ans.value === val)[0];
displayCorrect(ans.correct);
//Toggles message to true if answer is correct
ans.correct === true ? setIsCorrect(true) : setIsCorrect(false);
}
function Quiz(props) {
return (
<div className="quiz">
<div className="quesiton" role="h2">
{props.question}
</div>
<ul className="answers">{props.children}</ul>
</div>
);
}
function displayCorrect(correct) {
let correct_msg = correct ? "correct" : "incorrect";
console.log("Answer was " + correct_msg);
}
function nextQuestion() {
setIsCorrect(false); <== Should hide message when user selects "next question" button
if (document.querySelector('input[name="answer_group"]:checked') == null) {
alert("Must select an answer before proceeding to the next question");
return;
}
let val = document.querySelector('input[name="answer_group"]:checked')
.value;
let answerObj = question[counter].answers.filter(
(ans) => ans.value === val
)[0];
let updated_points = answerObj.correct ? points + 1 : points;
setPoints(updated_points);
let nextQuestion = counter + 1;
if (counter < question.length - 1) {
setCounter(nextQuestion);
} else {
setCounter(0);
}
displayCorrect(answerObj.correct);
}
return (
<div className="Quiz slide-top">
{!is_started ? (
<div className="start-intro-wrapper">
<h1 className="name">Quiz App</h1>
<Starter start={start} />
</div>
) : (
<div className="quick-wrapper slide-in-bottom">
<Quiz question={question[counter].question}>
{question[counter].answers.map((answer, index, arr) => {
return (
<Answer
key={index}
index={index}
answer={answer.value}
correct={answer.correct}
/>
);
})}
</Quiz>
<div className="answer-controls">
{isCorrect === true ? <p>You got it right!</p> : null} <== Messaging should show if user has selected correct message if correct option is selected
<button onClick={(e) => nextQuestion()}>
Next question
</button>
</div>
</div>
)}
</div>
);
}
Codesandbox Link

It doesn't display anything because you put null in the other condition for the display.
If you replace it with {isCorrect === true ? <p>You got it right!</p> : <p>You got it wrong!</p>} the correct message is displayed.
You can also remove completly the function displayCorrect it's only writing in the console.
If you want to clear the message when the user click on "next question" you could do it with a new variable hasAnswered set at false by default.
You set it to true in your checkAnswer function, and to false in your nextQuestion function.
The code for the text at the bottom would then looks like:
{hasAnswered &&
(isCorrect === true ? <p>You got it right!</p> : <p>You got it wrong!</p>)
}
Regarding the issue with you needing to click twice to update the radio button selected, i think it's a re-render issue when isCorrect change.
To avoid the issue, you could store the value checked by the user and use this to display if the radio should be checked or no.
It works with the following changes
let [isChecked, setChecked] = useState(null);
[...]
function Answer(props) {
return (
<li aria-labelledby="answers-list">
<label>
<input
checked={isChecked===props.answer}
type="radio"
name="answer_group"
className="answer"
value={props.answer}
onChange={checkAnswer}
/>
{props.answer}
</label>
</li>
);
}
function checkAnswer(e) {
let val = e.target.value;
let ans = question[counter].answers.filter((ans) => ans.value === val)[0];
setIsCorrect(ans.correct);
setChecked(ans.value);
}
You also need setChecked(null) in your nextQuestion function to reset everything.

onFocus and onBlur events for multiple elements

I'm trying to handle the onFocus and onBlur events for 2 elements - the input and the textarea elements. I even tried to implement it as one state with the object but it's just not possible, so I separated it into two states. Whenever I try to focus on the textarea, it'll expand, however, if I start focusing on the input element, it'll collapse instead of staying expanded. How do I implement this?
const [titleFocused, setTitleFocus] = useState(null);
const [contentFocused, setContentFocus] = useState(null);
function handleFocus(event) {
const {name} = event.target;
setTitleFocus(name === 'title' && true);
setContentFocus(name === 'content' && true);
}
function handleUnfocus(event) {
const {name} = event.target;
setTitleFocus(name === 'title' && false);
setContentFocus(name === 'content' && false);
}
return (
<div >
<form
className="create-note">
{titleFocused || contentFocused && (
<input
name="title"
onChange={handleChange}
value={note.title}
placeholder="Title"
onFocus={handleFocus}
onBlur={handleUnfocus}
/>)
}
<textarea
name="content"
onChange={handleChange}
value={note.content}
placeholder="Take a note..."
onFocus={handleFocus}
onBlur={handleUnfocus}
rows={titleFocused || contentFocused ? "3" : "1"}
/>
<Zoom in={titleFocused || contentFocused} appear={true}>
<Fab onClick={submitNote}>
<AddIcon fontSize="large" />
</Fab>
</Zoom>
</form>
</div>
);

Probably caused by event handles toggling both states even when the event is not concerning the component.
This should work
function handleFocus(event) {
const {name} = event.target;
name === 'title' && setTitleFocus(true);
name === 'content' && setContentFocus(true);
}
function handleUnfocus(event) {
const {name} = event.target;
name === 'title' && setTitleFocus(false);
name === 'content' && setContentFocus( false);
}

Formik instant feedback input box

I'm trying to make a input box component that has instant feedback using Formik. I want the input box to turn green when the user input matches a predefined string (the "answer"), gray if the input matches the prefix of the answer (including the empty string) and red otherwise. This string is stored as a property of the initial values, values.answer. The Formik validate function checks if the input equals values.answer and sets values.correct = true. I then created a css class corresponding to a green input box and set the className of the input conditional on the value of values.correct. The problem is it only seems to update (i.e turn green with a correct input) when I click out of focus of the input box (i.e onBlur). I would like it to work onChange. How would I do this?
Here is the relevant code sandbox: https://codesandbox.io/s/instant-feedback-box-lub0g?file=/src/Frame.js

Cool problem, but you've overcomplicated your code a little bit 😉 Some feedback:
touched is set to true during onBlur by default. You can override this by using setTouched(), but I found it simpler to just use values instead of touched in your form
try to keep values as minimal as possible, it's only meant to access input values so there's no need for hint and answer to be assigned to it
the purpose of the validation function is to return an errors object and not to set values, so remove assignments like values.correct = true
You don't need to store isDisabled in state, you can derive it from formik.submitCount and formik.isSubmitting
const Note = () => {
const [showFrame, setShowFrame] = useState({ 1: true });
const onCorrectSubmission = (frameId) => {
setShowFrame({ ...showFrame, [frameId]: true });
};
const text =
"What is the sum of the first three natural numbers? (give answer as a word, i.e one, two etc.)";
const hint = "The first three natural numbers are 1, 2, and 3";
const answer = "six";
return (
<div>
<h1>Induction</h1>
{showFrame[1] ? (
<Frame
id={1}
text={text}
hint={hint}
answer={answer}
onCorrectSubmission={onCorrectSubmission}
/>
) : null}
{showFrame[2] ? (
<Frame
id={2}
text={text}
hint={hint}
answer={answer}
onCorrectSubmission={onCorrectSubmission}
/>
) : null}
</div>
);
};
const Frame = ({
id,
text,
hint,
answer,
values,
onCorrectSubmission,
...props
}) => {
const validate = (values) => {
const errors = {};
if (!answer.startsWith(values.cloze)) {
errors.cloze = hint;
} else if (values.cloze !== answer) {
errors.cloze = true;
}
return errors;
};
const formik = useFormik({
initialValues: {
cloze: ""
},
validate,
onSubmit: (values) => {
onCorrectSubmission(id + 1);
}
});
const isFinished = formik.isSubmitting || formik.submitCount > 0;
return (
<form enablereinitialize={true} onSubmit={formik.handleSubmit}>
<p>{text}</p>
<input
id="cloze"
name="cloze"
type="text"
autoComplete="off"
{...formik.getFieldProps("cloze")}
disabled={isFinished}
className={`input
${!answer.startsWith(formik.values.cloze) ? "invalid-input" : ""}
${formik.values.cloze && !formik.errors.cloze ? "valid-input" : ""}
`}
/>
{formik.values.cloze && formik.errors.cloze ? (
<div>{formik.errors.cloze}</div>
) : null}
<button disabled={!!formik.errors.cloze || isFinished} type="submit">
Submit
</button>
</form>
);
};
export default Frame;
Live Demo

React - Input not working when using onChange and onKeyDown

I tried to implement something like a multi-select, where the user can either select a value from a data list or can type in a new value. A chosen value should be added to an array if the user presses enter. For detecting changes in the input field I use onChange and a state variable that saves the current value typed in. For detecting the press of enter I use onKeyDown. The problem is that I'm no longer able to type something in the input field, however choosing values from the data list works. I figured out that when I comment out onKeyDown, I can type something in the input field and can also choose from values provided by the data list. However, in this case, adding values to an array on the press of enter doesn't work. I'm fairly new to React, is there something I miss?
My current code looks like follows:
const EditableMultiSelect = ({ field, helpers, metadataField, editMode, setEditMode }) => {
const { t } = useTranslation();
const [inputValue, setInputValue] = useState('');
const handleChange = e => {
const itemValue = e.target.value;
setInputValue(itemValue);
}
const handleKeyDown = event => {
event.preventDefault();
if (event.keyCode === 13) {
field.value[field.value.length] = inputValue;
helpers.setValue(field.value);
setInputValue("");
}
}
const removeItem = () => {
console.log('to be implemented');
}
return (
editMode ? (
<>
<div
onBlur={() => setEditMode(false)}
ref={childRef}>
<input name="inputValue"
value={inputValue}
type="text"
onKeyDown={e => handleKeyDown(e)}
onChange={e => handleChange(e)}
placeholder={t('EDITABLE.MULTI.PLACEHOLDER')}
list="data-list"
/>
<datalist id="data-list">
{metadataField.collection.map((item, key) => (
<option key={key}>{t(item.value)}</option>
))}
</datalist>
</div>
{(field.value instanceof Array && field.value.length !== 0) ? (field.value.map((item, key) => (
<span className="ng-multi-value"
key={key}>
{t(item)}
<a onClick={() => removeItem(key)}>
<i className="fa fa-times" />
</a>
</span>
))) : null}
</>
) : (
<div onClick={() => setEditMode(true)}>
{(field.value instanceof Array && field.value.length !== 0) ? (
<ul>
{field.value.map((item, key) => (
<li key={key}>
<span>{item}</span>
</li>
))}
</ul>
) : (
<span className="editable preserve-newlines">
{""}
</span>
)}
<i className="edit fa fa-pencil-square"/>
</div>
)
);
};

You're calling event.preventDefault() every time a key is pressed. You should move it inside the if statement:
const handleKeyDown = event => {
if (event.keyCode === 13) {
event.preventDefault();
field.value[field.value.length] = inputValue;
helpers.setValue(field.value);
setInputValue("");
}
}

you can't type anything anymore in the input text because in the handleKeyDown event handler, you're calling event.preventDefault() in the early lines. So i think you just have to move it into the if case:
const handleKeyDown = event => {
if (event.keyCode === 13) {
event.preventDefault();
field.value[field.value.length] = inputValue;
helpers.setValue(field.value);
setInputValue("");
}
}

Remove e.preventDefault() or put it inside the if statements.
It is the one preventing the input from being editable.