A hook to use immer as a React hook to manipulate state.
npm install immer use-immer
useImmer(initialState) is very similar to useState.
The function returns a tuple, the first value of the tuple is the current state, the second is the updater function,
which accepts an immer producer function or a value as argument.
When passing a function to the updater, the draft argument can be mutated freely, until the producer ends and the changes will be made immutable and become the next state.
Example: https://codesandbox.io/s/l97yrzw8ol
import React from "react";
import { useImmer } from "use-immer";
function App() {
const [person, updatePerson] = useImmer({
name: "Michel",
age: 33
});
function updateName(name) {
updatePerson(draft => {
draft.name = name;
});
}
function becomeOlder() {
updatePerson(draft => {
draft.age++;
});
}
return (
<div className="App">
<h1>
Hello {person.name} ({person.age})
</h1>
<input
onChange={e => {
updateName(e.target.value);
}}
value={person.name}
/>
<br />
<button onClick={becomeOlder}>Older</button>
</div>
);
}(obviously, immer is a little overkill for this example)
When passing a value to the updater instead of a function, useImmer hook behaves the same as useState hook and updates the state with that value.
import React from 'react';
import { useImmer } from 'use-immer';
function BirthDayCelebrator(){
const [age, setAge] = useImmer(20);
function birthDay(event){
setAge(age + 1);
alert(`Happy birthday #${age} Anon! hope you good`);
}
return(
<div>
<button onClick={birthDay}>It is my birthday</button>
</div>
);
}Obviously if you have to deal with immutability it is better option passing a function to the updater instead of a direct value.
Immer powered reducer, based on useReducer hook
Example: https://codesandbox.io/s/2zor1monvp
import React from "react";
import { useImmerReducer } from "use-immer";
const initialState = { count: 0 };
function reducer(draft, action) {
switch (action.type) {
case "reset":
return initialState;
case "increment":
return void draft.count++;
case "decrement":
return void draft.count--;
}
}
function Counter() {
const [state, dispatch] = useImmerReducer(reducer, initialState);
return (
<>
Count: {state.count}
<button onClick={() => dispatch({ type: "reset" })}>Reset</button>
<button onClick={() => dispatch({ type: "increment" })}>+</button>
<button onClick={() => dispatch({ type: "decrement" })}>-</button>
</>
);
}
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