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how useReducer works

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Spotless Shark answered on June 21, 2020 Popularity 6/10 Helpfulness 1/10

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# react
import "./styles.css";
import React, { useReducer } from "react";

function redcuer(state, action){
  return { count: state.count + 1 }
}

export default function App() {
  const [state, dispatch] = useReducer(redcuer, { count: 0 })

  function decrement(){

  }
  function increment(){
    dispatch()
  }
  return (
    <div className="App">
      <button onClick={decrement}>-</button>
      <span>{state.count}</span>
      <button onClick={increment}>+</button>
    </div>
  );
}

Popularity 6/10 Helpfulness 1/10 Language javascript

Source: www.delftstack.com

Tags: javascript use-reducer

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Contributed on Sep 15 2022

Spotless Shark

0 Answers Avg Quality 2/10

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useReducer

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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

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Contributed on Jun 21 2020

Dangerous Dunlin

0 Answers Avg Quality 2/10

useReducer

Comment

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

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Contributed on Jun 19 2022

fawad ahmed

0 Answers Avg Quality 2/10

useReducer example

Comment

import React, { useReducer } from 'react';

// Reducer fonksiyonu
const reducer = (state, action) => {
  switch (action.type) {
    case 'INCREMENT':
      return { count: state.count + 1 };
    case 'DECREMENT':
      return { count: state.count - 1 };
    default:
      return state;
  }
};

// Komponent
const Counter = () => {
  // Başlangıç durumu ve reducer'ı kullanarak state'i tanımla
  const initialState = { count: 0 };
  const [state, dispatch] = useReducer(reducer, initialState);

  return (
    <div>
      <p>Count: {state.count}</p>
      <button onClick={() => dispatch({ type: 'INCREMENT' })}>Increment</button>
      <button onClick={() => dispatch({ type: 'DECREMENT' })}>Decrement</button>
    </div>
  );
};

export default Counter;

Popularity 7/10 Helpfulness 4/10 Language python

Source: chat.openai.com

Tags: python use-reducer u

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Contributed on Dec 14 2023

Davut Bilgic

0 Answers Avg Quality 2/10

usereducer

Comment

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

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Contributed on Jun 16 2022

Blue Baboon

0 Answers Avg Quality 2/10

useReducer

Comment

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

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Contributed on Jul 17 2023

Cloudy Crocodile

0 Answers Avg Quality 2/10

usereducer

Comment

import { useReducer } from 'react';

function reducer(state, action) {
  // ...
}

function MyComponent() {
  const [state, dispatch] = useReducer(reducer, { age: 42 });
  // ...

Popularity 8/10 Helpfulness 2/10 Language javascript

Source: react.dev

Tags: javascript j

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Contributed on Apr 16 2023

Mikiyas Kelifa

0 Answers Avg Quality 2/10

useReducer

Comment

import { useReducer } from 'react';
import AddTask from './AddTask.js';
import TaskList from './TaskList.js';

function tasksReducer(tasks, action) {
  switch (action.type) {
    case 'added': {
      return [...tasks, {
        id: action.id,
        text: action.text,
        done: false
      }];
    }
    case 'changed': {
      return tasks.map(t => {
        if (t.id === action.task.id) {
          return action.task;
        } else {
          return t;
        }
      });
    }
    case 'deleted': {
      return tasks.filter(t => t.id !== action.id);
    }
    default: {
      throw Error('Unknown action: ' + action.type);
    }
  }
}

export default function TaskApp() {
  const [tasks, dispatch] = useReducer(
    tasksReducer,
    initialTasks
  );

  function handleAddTask(text) {
    dispatch({
      type: 'added',
      id: nextId++,
      text: text,
    });
  }

  function handleChangeTask(task) {
    dispatch({
      type: 'changed',
      task: task
    });
  }

  function handleDeleteTask(taskId) {
    dispatch({
      type: 'deleted',
      id: taskId
    });
  }

  return (
    <>
      <h1>Prague itinerary</h1>
      <AddTask
        onAddTask={handleAddTask}
      />
      <TaskList
        tasks={tasks}
        onChangeTask={handleChangeTask}
        onDeleteTask={handleDeleteTask}
      />
    </>
  );
}

let nextId = 3;
const initialTasks = [
  { id: 0, text: 'Visit Kafka Museum', done: true },
  { id: 1, text: 'Watch a puppet show', done: false },
  { id: 2, text: 'Lennon Wall pic', done: false }
];

Popularity 7/10 Helpfulness 2/10 Language javascript

Source: react.dev

Tags: javascript use-reducer use-reduce

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Contributed on Feb 18 2024

Vivacious Vulture

0 Answers Avg Quality 2/10

useReducer

Comment

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

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

Popularity 10/10 Helpfulness 2/10 Language javascript

Source: reactjs.org

Tags: javascript j

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Contributed on Jun 21 2020

Dangerous Dunlin

0 Answers Avg Quality 2/10

usereducer

Comment

  const [state, dispatch] = useReducer(
    reducer,
    {count: initialCount}  );

Popularity 10/10 Helpfulness 1/10 Language javascript

Source: reactjs.org

Tags: javascript j

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Contributed on Jan 17 2021

Depressed Dragonfly

0 Answers Avg Quality 2/10

useReducer

Comment

function reducer(state, action) {
  switch (action.type) {
    case 'incremented_age': {
      // ✅ Instead, return a new object
      return {
        ...state,
        age: state.age + 1
      };
    }

Popularity 9/10 Helpfulness 1/10 Language javascript

Source: Grepper

Tags: javascript j

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Contributed on Nov 02 2022

Bimlendra Ray

0 Answers Avg Quality 2/10

how useReducer works

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