what is usereducer in react

Comment

14

useReducer is a hook in React that allows you to manage state in your components. It is similar to useState, but it is designed for managing state that is more complex or requires the ability to perform more than just simple state updates.

Here is an example of how useReducer might be used:

const [state, dispatch] = useReducer(reducer, initialState);
//In this example, useReducer takes two arguments: a "reducer" 
//function and an initial state. The reducer is a function that takes 
//in the current state and an action, and returns a new state. 
//The initial state is the state that the component will start with.

//The useReducer hook returns an array with two elements: 
//the current state and a dispatch function. The dispatch function is 
//used to send actions to the reducer, which will then update the state.

//Here is an example of how the reducer function might look:
function reducer(state, action) {
  switch (action.type) {
    case 'INCREMENT':
      return {count: state.count + 1};
    case 'DECREMENT':
      return {count: state.count - 1};
    default:
      return state;
  }
}
// In this example, the reducer function is handling two actions: 
// INCREMENT and DECREMENT. When the INCREMENT action is dispatched, 
//the reducer will return a new state with the count field incremented by 1.
//When the DECREMENT action is dispatched, the reducer will return a new state with the count field decremented by 1.

// To continue using the useReducer hook in your component, you can call 
//the dispatch function with an action object as an argument. For example:

dispatch({type: 'INCREMENT'});
//This will cause the reducer function to be called with the INCREMENT action, 
//which will update the state and cause the component to re-render.

//You can also use the current state and the dispatch function in your 
//component's JSX:
<button onClick={() => dispatch({type: 'INCREMENT'})}>Increment</button>
<p>Count: {state.count}</p>
// In this example, clicking the "Increment" button will dispatch the INCREMENT action, 
//which will update the state and cause the component to re-render with the updated count.

Popularity 10/10 Helpfulness 4/10 Language javascript

Source: Grepper

Tags: javascript use-reducer

Share

Link to this answer
Share Copy Link

Contributed on Jan 05 2023

vip_codes

0 Answers Avg Quality 2/10

useReducer

Comment

38

const initialState = {count: 0};

function reducer(state, action) {
  switch (action.type) {
    case 'increment':
      return {count: state.count + 1};
    case 'decrement':
      return {count: state.count - 1};
    default:
      throw new Error();
  }
}

function Counter() {
  const [state, dispatch] = useReducer(reducer, initialState);
  return (
    <>
      Count: {state.count}
      <button onClick={() => dispatch({type: 'decrement'})}>-</button>
      <button onClick={() => dispatch({type: 'increment'})}>+</button>
    </>
  );
}

Popularity 10/10 Helpfulness 4/10 Language javascript

Source: reactjs.org

Tags: javascript j

Share

Link to this answer
Share Copy Link

Contributed on Jun 21 2020

Dangerous Dunlin

0 Answers Avg Quality 2/10

useReducer

Comment

6

import './App.css';
import { useState, useReducer } from 'react';


function reducer(state, action) {
  switch (action.type) {
    case 'increment':
      return ({ ...state, count: state.count + 1 })
    case 'decrement':
      return ({ ...state, count: state.count - 1 })
    case 'tgColor':
      return ({ ...state, color: (!state.color) })
    case 'handleInputChange':
      return ({ ...state, name: action.payload })
  }
}

function App() {

  const [state, dispatch] = useReducer(reducer, { count: 0, color: false, name: "" })

  // const [name, setName] = useState("")
  // const [count, setCount] = useState(0)
  // const [color, setColor] = useState(false);

  const handleInputChange = (e) => {
    dispatch({ type: "handleInputChange", payload: e.target.value })
  }

  const colorCode = "#b81f00";

  return (
    <div className="App">
      <form action="">
        <input type="text" onChange={handleInputChange} value={state.name} placeholder="Enter Name" />
      </form>
      <h3 style={state.color ? { color: "red" } : { color: "black" }}>{state.count}</h3>
      <button className="btn" onClick={() => dispatch({ type: "increment" })}>+</button>
      <button className="btn" onClick={() => dispatch({ type: "decrement" })}>-</button>
      <button className="btn" onClick={() => dispatch({ type: "tgColor" })}>Color</button>
      <h2 style={state.color ? { color: "red" } : { color: "black" }}>{state.name}</h2>
    </div>
  );
}

export default App;

Popularity 10/10 Helpfulness 4/10 Language javascript

Source: Grepper

Tags: javascript j

Share

Link to this answer
Share Copy Link

Contributed on Jun 19 2022

fawad ahmed

0 Answers Avg Quality 2/10

usereducer hook react

Comment

19

import React, { useReducer } from 'react'
import { render } from 'react-dom'

const types = {
  PET: 'PET',
  COLOR: 'COLOR',
}

const reducer = (state, action) => {
  switch (action.type) {
    case types.PET:
      return { ...state, pet: action.value }
    case types.COLOR:
      return { ...state, color: action.value }
  }
}

const initialState = {
  color: 'black',
  pet: 'cat',
}

export default function App() {
  const [state, dispatch] = useReducer(reducer, initialState)

  return (
    <div>
      <label>Choose a color and a pet: </label>
      <br />
      <select
        value={state.color}
        onChange={event => {
          dispatch({ type: types.COLOR, value: event.target.value })
        }}
      >
        <option value="black">Black</option>
        <option value="pink">Pink</option>
        <option value="blue">Blue</option>
      </select>
      <select
        value={state.pet}
        onChange={event => {
          dispatch({ type: types.PET, value: event.target.value })
        }}
      >
        <option value="cat">Cat</option>
        <option value="dog">Dog</option>
        <option value="mouse">Mouse</option>
      </select>
      <br />
      <br />
      You chose a {state.color} {state.pet}
    </div>
  )
}

render(<App />, document.querySelector('#app'))

Popularity 10/10 Helpfulness 4/10 Language javascript

Source: www.react.express

Tags: hook

Share

Link to this answer
Share Copy Link

Contributed on Nov 08 2022

Mehedi Islam Ripon

0 Answers Avg Quality 2/10

useReducer React

Comment

1

import React, { useReducer } from "react";

const reducer = (state, action) => {
  switch (action.type) {
    case "increment":
      return { count: state.count + 1 };
      break;
    case "decrement":
      return { count: state.count - 1 };
      break;
    default:
      throw new Error();
  }
};

const UseReduceExample = () => {
  const [state, dispatch] = useReducer(reducer, initialCount );

  return (
    <>
      Count: {state.count}
      <button onClick={() => dispatch({ type: "increment" })}>+</button>
    </>
  );
};

export default UseReduceExample;

Popularity 9/10 Helpfulness 4/10 Language javascript

Source: stackoverflow.com

Tags: javascript j

Share

Link to this answer
Share Copy Link

Contributed on May 23 2022

Mateo Jaramillo

0 Answers Avg Quality 2/10

usereducer

Comment

0

import React from "react";
import { useReducer } from "react";
const initialState = {
  count: 0,
};
type ReducerProps = {
  state: any;
};
const reducer = (state: state, action) => {
  switch (action.type) {
    case "increment":
      return { count: state.count + action.payload };
    case "decrement":
      return { count: state.count - action.payload };
    default:
      return state;
  }
};

const Counter = () => {
  const [state, dispatch] = useReducer(reducer, initialState);
  return (
    <div>
      Count : {state.count}
      <button
        onClick={() => {
          dispatch({ type: "increment", payload: 1 });
        }}
      >
        Increment ++
      </button>
      <button
        onClick={() => {
          dispatch({ type: "decrement", payload: 1 });
        }}
      >
        Decrement --
      </button>
    </div>
  );
};

export default Counter;

Popularity 9/10 Helpfulness 3/10 Language javascript

Source: Grepper

Tags: javascript j

Share

Link to this answer
Share Copy Link

Contributed on Jun 16 2022

Blue Baboon

0 Answers Avg Quality 2/10

useReducer React

Comment

0

import React, { useReducer } from "react";

const reducer = (state, action) => {
  switch (action.type) {
    case "increment":
      return { count: state.count + 1 };
      break;
    case "decrement":
      return { count: state.count - 1 };
      break;
    default:
      throw new Error();
  }
};

const UseReduceExample = () => {
  const [state, dispatch] = useReducer(reducer, initialCount );

  return (
    <>
      Count: {state.count}
      <button onClick={() => dispatch({ type: "increment" })}>+</button>
    </>
  );
};

export default UseReduceExample;

Popularity 9/10 Helpfulness 3/10 Language javascript

Source: stackoverflow.com

Tags: javascript j

Share

Link to this answer
Share Copy Link

Contributed on May 23 2022

Mateo Jaramillo

0 Answers Avg Quality 2/10

useReducer React

Comment

0

import React, { useReducer } from "react";

const reducer = (state, action) => {
  switch (action.type) {
    case "increment":
      return { count: state.count + 1 };
      break;
    case "decrement":
      return { count: state.count - 1 };
      break;
    default:
      throw new Error();
  }
};

const UseReduceExample = () => {
  const [state, dispatch] = useReducer(reducer, initialCount );

  return (
    <>
      Count: {state.count}
      <button onClick={() => dispatch({ type: "increment" })}>+</button>
    </>
  );
};

export default UseReduceExample;

Popularity 9/10 Helpfulness 3/10 Language javascript

Source: stackoverflow.com

Tags: javascript j

Share

Link to this answer
Share Copy Link

Contributed on May 23 2022

Mateo Jaramillo

0 Answers Avg Quality 2/10

useReducer

Comment

0

import React, { useReducer } from 'react';

const reducer = (state, action) => {
  // Logic to update the state based on the action type and payload
  switch (action.type) {
    case 'INCREMENT':
      return { count: state.count + 1 };
    case 'DECREMENT':
      return { count: state.count - 1 };
    // Handle other action types here
    default:
      return state;
  }
};

const initialState = { count: 0 };

const Counter = () => {
  const [state, dispatch] = useReducer(reducer, initialState);

  const increment = () => {
    dispatch({ type: 'INCREMENT' });
  };

  const decrement = () => {
    dispatch({ type: 'DECREMENT' });
  };

  return (
    <div>
      <p>Count: {state.count}</p>
      <button onClick={increment}>Increment</button>
      <button onClick={decrement}>Decrement</button>
    </div>
  );
};

Popularity 8/10 Helpfulness 2/10 Language javascript

Source: chat.openai.com

Tags: javascript j

Share

Link to this answer
Share Copy Link

Contributed on Jul 17 2023

Cloudy Crocodile

0 Answers Avg Quality 2/10

useReducer React

Comment

0

import React, { useReducer } from "react";

const reducer = (state, action) => {
  switch (action.type) {
    case "increment":
      return { count: state.count + 1 };
      break;
    case "decrement":
      return { count: state.count - 1 };
      break;
    default:
      throw new Error();
  }
};

const UseReduceExample = () => {
  const [state, dispatch] = useReducer(reducer, initialCount );

  return (
    <>
      Count: {state.count}
      <button onClick={() => dispatch({ type: "increment" })}>+</button>
    </>
  );
};

export default UseReduceExample;

Popularity 9/10 Helpfulness 2/10 Language javascript

Source: stackoverflow.com

Tags: javascript j

Share

Link to this answer
Share Copy Link

Contributed on May 23 2022

Mateo Jaramillo

0 Answers Avg Quality 2/10

what is usereducer in react

Contents

More Related Answers