Sometimes, we have to manage the status in the react state.
For example, we have a submit form, and we have to manage the status of the form.
There are many way to express the status.
I will introduce the bad example to express status.
Bad example
1. Use the object to express the status.
const Page = () => {
const [status, setStatus] = useState<{ loading: boolean, error: boolean, success: boolean }>({ loading: false, error: false, success: false });
const fetchUser = async () => {
setStatus({ loading: true, error: false, success: false });
try {
const user = await api.getUser();
setStatus({ loading: false, error: false, success: true });
} catch (e) {
setStatus({ loading: false, error: true, success: false });
}
};
return (
<>
{status.loading && <div>Loading...</div>}
{status.error && <div>Error...</div>}
{status.success && <div>Success...</div>}
<button onClick={fetchUser}>Fetch</button>
</>
);
};
This is bad example because the status is very complex.
When you update the status, you have to update all the status.
There are only three status pattern in this example.
// loading
setStatus({ loading: true, error: false, success: false });
// success
setStatus({ loading: false, error: false, success: true });
// error
setStatus({ loading: false, error: true, success: false });
But when you use a object to express the status, reader can't understand that there are only three patterns.
So this is bad example.
2. use index to express the status.
const Page = () => {
const [status, setStatus] = useState<0 | 1 | 2 | 3>(3);
const [user, setUser] = useState<User | null>(null);
const fetchUser = async () => {
setStatus(0);
try {
const user = await api.getUser();
setUser(user);
setStatus(2);
} catch (e) {
setStatus(1);
}
};
const reset = () => {
setUser(null);
setStatus(3);
};
return (
<>
{status === 0 && <div>Loading...</div>}
{status === 1 && <div>Error...</div>}
{status === 2 && <div>{user?.name}</div>}
<button onClick={fetchUser}>Fetch</button>
<button onClick={reset}>Reset</button>
</>
);
};
This is a very simple example.
But there are also have a problem in this example.
When you use the index to express the status, you have to remember the status number.
If when you have to add a new status, you have to update all the status number.
So, this is also not good example.
3. create state for each status.
const Page = () => {
const [loading, setLoading] = useState<boolean>(false);
const [error, setError] = useState<boolean>(false);
const [success, setSuccess] = useState<boolean>(false);
const [user, setUser] = useState<User | null>(null);
const fetchUser = async () => {
setLoading(true);
try {
const user = await api.getUser();
setUser(user);
setSuccess(true);
} catch (e) {
setError(true);
}
};
const reset = () => {
setUser(null);
setLoading(false);
setError(false);
setSuccess(false);
};
return (
<>
{loading && <div>Loading...</div>}
{error && <div>Error...</div>}
{success && <div>{user?.name}</div>}
<button onClick={fetchUser}>Fetch</button>
<button onClick={reset}>Reset</button>
</>
);
};
This is also not good example.
You have to management all the status state in the function all the time.
And if you forget to update the status, it will be a bug.
Reset function is also very complex.
Recommendation
- Use the string to express the status.
const Page = () => {
const [status, setStatus] = useState<'loading' | 'error' | 'success' | 'idle'>('idle');
const [user, setUser] = useState<User | null>(null);
const fetchUser = async () => {
setStatus('loading');
try {
const user = await api.getUser();
setUser(user);
setStatus('success');
} catch (e) {
setStatus('error');
}
};
const reset = () => {
setUser(null);
setStatus('idle');
};
return (
<>
{status === 'loading' && <div>Loading...</div>}
{status === 'error' && <div>Error...</div>}
{status === 'success' && <div>{user?.name}</div>}
<button onClick={fetchUser}>Fetch</button>
<button onClick={reset}>Reset</button>
</>
);
};
This is a very simple example.
And you can understand the status easily.
When you have to add a new status, you can add a new status easily.
Of course there are cons in this example.
You cannot express the status in the loading and success status in the same time.
But I thought this is not a big problem.
So if you manage the status in the react state, I recommend to use the string to express the status.
Conclusion
When you manage the status in the react state, use the string to express the status.
This is very simple and easy to understand.
And you can add a new status easily.
If you use the object or index to express the status, you have to update all the status when you add a new status.
So, I recommend to use the string to express the status.
Thank you for reading.
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