use-immer

A hook to use immer as a React hook to manipulate state.

Installation

npm install immer use-immer

API

useImmer

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.

Managing state with immer producer function

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

1import React from "react";
2import { useImmer } from "use-immer";
3
4
5function App() {
6  const [person, updatePerson] = useImmer({
7    name: "Michel",
8    age: 33
9  });
10
11  function updateName(name) {
12    updatePerson(draft => {
13      draft.name = name;
14    });
15  }
16
17  function becomeOlder() {
18    updatePerson(draft => {
19      draft.age++;
20    });
21  }
22
23  return (
24    <div className="App">
25      <h1>
26        Hello {person.name} ({person.age})
27      </h1>
28      <input
29        onChange={e => {
30          updateName(e.target.value);
31        }}
32        value={person.name}
33      />
34      <br />
35      <button onClick={becomeOlder}>Older</button>
36    </div>
37  );
38}

(obviously, immer is a little overkill for this example)

Managing state as simple useState hook

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.

1import React from 'react';
2import { useImmer } from 'use-immer';
3
4function BirthDayCelebrator(){
5  const [age, setAge] = useImmer(20);
6
7  function birthDay(event){
8    setAge(age + 1);
9    alert(`Happy birthday #${age} Anon! hope you good`);
10  }
11
12  return(
13    <div>
14      <button onClick={birthDay}>It is my birthday</button>
15    </div>
16  );
17}

Obviously if you have to deal with immutability it is better option passing a function to the updater instead of a direct value.

useImmerReducer

Immer powered reducer, based on useReducer hook

Example: https://codesandbox.io/s/2zor1monvp

1import React from "react";
2import { useImmerReducer } from "use-immer";
3
4const initialState = { count: 0 };
5
6function reducer(draft, action) {
7  switch (action.type) {
8    case "reset":
9      return initialState;
10    case "increment":
11      return void draft.count++;
12    case "decrement":
13      return void draft.count--;
14  }
15}
16
17function Counter() {
18  const [state, dispatch] = useImmerReducer(reducer, initialState);
19  return (
20    <>
21      Count: {state.count}
22      <button onClick={() => dispatch({ type: "reset" })}>Reset</button>
23      <button onClick={() => dispatch({ type: "increment" })}>+</button>
24      <button onClick={() => dispatch({ type: "decrement" })}>-</button>
25    </>
26  );
27}