useReducer() hook react

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code snippet 

https://codesandbox.io/s/usereducer-demo-zxguu?file=/src/App.js

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Contributed on Nov 02 2021

Confused Crossbill

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what is usereducer in react

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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.

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Contributed on Jan 05 2023

vip_codes

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usereducer hook react

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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'))

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Source: www.react.express

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Contributed on Nov 08 2022

Mehedi Islam Ripon

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useReducer React

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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;

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Source: stackoverflow.com

Tags: javascript j

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Contributed on May 23 2022

Mateo Jaramillo

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useReducer React

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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;

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Source: stackoverflow.com

Tags: javascript j

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Contributed on May 23 2022

Mateo Jaramillo

0 Answers Avg Quality 2/10

useReducer React

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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;

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Source: stackoverflow.com

Tags: javascript j

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Contributed on May 23 2022

Mateo Jaramillo

0 Answers Avg Quality 2/10

useReducer React

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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;

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Source: stackoverflow.com

Tags: javascript j

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Contributed on May 23 2022

Mateo Jaramillo

0 Answers Avg Quality 2/10

useReducer React

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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;

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Source: stackoverflow.com

Tags: javascript j

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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;

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Source: stackoverflow.com

Tags: javascript j

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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;

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Source: stackoverflow.com

Tags: javascript j

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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 2/10 Language javascript

Source: stackoverflow.com

Tags: javascript j

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Contributed on May 23 2022

Mateo Jaramillo

0 Answers Avg Quality 2/10

useReducer() hook react

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