How to find display error message from API in reactjs - reactjs

Question

I'm new to React.JS, creating an app for contacts. From API, the fields of contact got validated, if same name or phone number exists then it will show error message in API. My query is how to show the error message in UI while entering the same name or phone number. Do I need to fetch from Contact API? If yes, I could fetch the API of contacts in DIdmount but don't know how to show the error? Can any one help me in this?

Answer 1

Create a state variable for error with the initial value set to "" or null. Make the api call, the server (assuming you are also building the server) should check to see if the name and phone number already exist. If they already exist the server should return an error. In your react app catch the error after your API call and assign it to your state variable for error. Here is an example for the client using hooks.
export default function RegistrationForm(props) {
const [error, setError] = useState(null)
const errorDiv = error
? <div className="error">
<i class="material-icons error-icon">error_outline</i>
{error}
</div>
: '';
const handleSubmit = e => {
e.preventDefault();
setError(null);
const { full_name, user_name, password } = e.target;
AuthApiService.postUser({
full_name: full_name.value,
user_name: user_name.value,
password: password.value
})
.then(user => {
full_name.value = '';
user_name.value = '';
password.value = '';
props.onRegistrationSuccess();
})
.catch(res => {
setError(res.error);
})
};
return(
<form className='RegistrationForm'
onSubmit={handleSubmit}
>
<div className='full_name'>
<label htmlFor='RegistrationForm__full_name'>
Full name
</label>
<Input
name='full_name'
type='text'
required
id='RegistrationForm__full_name'>
</Input>
</div>
<div className='user_name'>
<label htmlFor='RegistrationForm__user_name'>
User name
</label>
<Input
name='user_name'
type='text'
required
id='RegistrationForm__user_name'>
</Input>
</div>
<div className='password'>
<label htmlFor='RegistrationForm__password'>
Password
</label>
<Input
name='password'
type='password'
required
id='RegistrationForm__password'
>
</Input>
</div>
<div className='confirm-password'>
<label htmlFor="LoginForm__confirm-password">
Retype Password
</label>
<Input
name='confirm-password'
type="password"
required
id="LoginForm__confirm-password">
</Input>
</div>
{errorDiv}
<Button type='submit' variant='contained' color='default'>
Register
</Button>
</form>
)
}

Answer 2

Yes if you want exact error message from api response than you can get this by
.then(responseJson=> { console.log(responseJson.response.data.message) })

Answer 3

Have an API to check if the name is available or not, and hit the API when the user changes something in the input.
import React, { useState } from "react";
import ReactDOM from "react-dom";
let delayTimer;
function App() {
const [name, setName] = useState("");
const [nameAvailable, setNameAvailable] = useState(null);
async function checkNameAvailable() {
try {
const response = await APIUtility.isNameAvailable(name);
const { data = null } = response;
if (data) {
setNameAvailable(data); // data may be true or false
}
} catch (error) {
setNameAvailable(null);
}
}
function handleNameChange(e) {
setName(e.target.value);
if (name.length > 0) {
if (delayTimer) clearTimeout(delayTimer);
delayTimer = setTimeout(function() {
checkNameAvailable();
}, 1000); // Will do the ajax stuff after 1000 ms, or 1 s
}
}
return (
<form>
<label htmlFor="invite_code">Enter your name:</label>
<input
value={name}
onChange={handleNameChange}
type="text"
name="inviteCode"
id="invite_code"
autoComplete="off"
/>
{nameAvailable && <span>Name already taken</span>}
</form>
);
}
const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);