In this article, you are going to see a practical approach on how you can implement useReducer, and it also introduces the idea of reducer, so it's beginner-friendly!
So we have this form
import {
FormControl,
FormLabel,
FormHelperText,
Input,
Button
} from "@chakra-ui/react";
const Form = () => {
const [name, setName] = useState("");
const [email, setEmail] = useState("");
const [password, setPassword] = useState("");
return (
<FormControl id="form" p={50}>
<FormLabel>First and last name</FormLabel>
<Input
type="text"
value={name}
onChange={(e) => setName(e.target.value)}
/>
<FormLabel>Email address</FormLabel>
<Input
type="email"
value={email}
onChange={(e) => setEmail(e.target.value)}
/>
<FormHelperText>We'll never share your email.</FormHelperText>
<FormLabel>Password</FormLabel>
<Input
type="password"
value={password}
onChange={(e) => setPassword(e.target.value)}
/>
<Button mt={4} colorScheme="teal" type="submit">
Login
</Button>
</FormControl>
);
};
export default Form;
We are using Chakra UI, a React library, and in case you don't know how to install it, go here.
So the first thing we want to do is to create our initialState.
This will be an object containing our 3 states: name, email and password.
const initialState = {
name : '',
email : '',
password : ''
}
const Form = () => {
...
}
Now import the useReducer hook
import { useState, useReducer } from "react";
So here comes the new part for you if you are just learning the concept of reducer.
We are going to create a separate file called reducer.js where it will have a function that handles our state.
// reducer.js
function reducer (state, action) {
}
As you can see we take two parameters:
-
statethis will be the state we receive from the dispatch method that was executed in our case fromApp.js -
actionsomeone calls it theactionObjectbecause when dispatched it looks like this:
const action = {
type: 'FETCH'
data : "Alejo"
};
Continuing with the reducer function, now lets build our switch cases
function reducer (state, action) {
switch(action.type){
case "UPDATE" :
return {
...state,
[action.key] : action.value
}
default:
return state
}
}
So what's going on here?
The switch statement, which will be in charge of aligning the action.type to the changes the reducer is going to implement. In other words, the switch will determine those changes like modifying the state BASED on the value of the action.type
Are you getting it now?
The spread operator is ...state and what it does is basically copying the entire state, in order to only modify only the [action.key] : action.value
Having explained the above, now let's add the reducer function into the App.js component
import reducer from "./reducer"
import { useState, useReducer } from "react";
const initialState = {
name: "",
email: "",
password: ""
};
const Form = () => {
// const [name, setName] = useState("");
// const [email, setEmail] = useState("");
// const [password, setPassword] = useState("");
const [reducerState, dispatch] = useReducer(reducer, initialState);
...
}
Following that we are going to change value of our input from the useState, to the initialState and change the onChange setting state functions to the reducer ones using dispatch.
<Input
type="text"
value={reducerState.name}
onChange={(e) =>
dispatch({
type: "UPDATE",
value: e.target.value,
key: "name"
})
}
/>
<Input
type="email"
value={reducerState.email}
onChange={(e) =>
dispatch({
type: "UPDATE",
value: e.target.value,
key: "email"
})
}
/>
<Input
type="password"
value={reducerState.password}
onChange={(e) =>
dispatch({
type: "UPDATE",
value: e.target.value,
key: "password"
})
}
/>
Final step
Let's create a console.log inside a submit() function, so we get to see the complete state from the reducer, and confirm that we have refactored the form successfully:
const Form = () => {
function submit() {
console.log({
name: reducerState.name,
email: reducerState.email,
password: reducerState.password
});
}
return (
...
<Button onClick={() => submit()} mt={4} colorScheme="teal" type="submit">
Login
</Button>
);
};
export default Form;
OUTPUT:
{name: 'asadsasd', email: 'adsda@gmail.com', password: 'sadadada'}
Success! Now you have a React form working with useReducer
Complete refactored form code:
Couldn't post a Github repo, but you can check its CodeSandbox.
// App.js
import {
FormControl,
FormLabel,
FormHelperText,
Input,
Button
} from "@chakra-ui/react";
import reducer from "./reducer";
import { useState, useReducer } from "react";
const initialState = {
name: "",
email: "",
password: ""
};
const Form = () => {
const [reducerState, dispatch] = useReducer(reducer, initialState);
function submit() {
console.log({
name: reducerState.name,
email: reducerState.email,
password: reducerState.password
});
}
return (
<FormControl id="form" p={50}>
<FormLabel>First and last name</FormLabel>
<Input
type="text"
value={reducerState.name}
onChange={(e) =>
dispatch({
type: "UPDATE",
value: e.target.value,
key: "name"
})
}
/>
<FormLabel>Email address</FormLabel>
<Input
type="email"
value={reducerState.email}
onChange={(e) =>
dispatch({
type: "UPDATE",
value: e.target.value,
key: "email"
})
}
/>
<FormHelperText>We'll never share your email.</FormHelperText>
<FormLabel>Password</FormLabel>
<Input
type="password"
value={reducerState.password}
onChange={(e) =>
dispatch({
type: "UPDATE",
value: e.target.value,
key: "password"
})
}
/>
<Button onClick={() => submit()} mt={4} colorScheme="teal" type="submit">
Login
</Button>
</FormControl>
);
};
export default Form;
// reducer.js
function reducer (state, action) {
switch(action.type){
case "UPDATE" :
return {
...state,
[action.key] : action.value
}
default:
return state
}
}
export default reducer
This article was published originally in React Shark's blog:
https://www.reactshark.com/blog/form-refactor-with-usereducer
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