react-todo/App.js

import React, { Component } from 'react';
import './App.css';

import { connect, Provider } from 'react-redux';
import { createStore, combineReducers } from 'redux';



function todoReducer(state, action){
    if (typeof state === 'undefined'){
        return {items: JSON.parse(localStorage.todo || "[]")};
    }
    if (action.type === 'NEW_TODO'){
        console.log(state);
        return {items: [...state.items, {title: action.title, text: action.text, timestamp: (new Date()).getTime()}]}
    }
    if (action.type === 'DELETE_TODO'){
        let items = [];
        for (let i=0;i<state.items.length;i++){
            if (state.items[i].timestamp !== action.timestamp){
                items.push(state.items[i]);
            }
        }
        return {items};
    }
}

const reducers = combineReducers({
    todo: todoReducer,
})


var store = createStore(reducers)

store.subscribe(() => {
    let state = store.getState();
    localStorage.todo = JSON.stringify(state.todo.items);
})




class ToDoItem extends Component {
    constructor(props){
        super(props);
        this.delete = this.delete.bind(this);
    }
    delete() {
        store.dispatch({type: "DELETE_TODO", timestamp: this.props.item.timestamp})
    }

    render() {
        return (
            <div>
                <h3> { this.props.item.title } </h3>
                <p> { this.props.item.text }</p>
                <span> { (new Date(this.props.item.timestamp)).toLocaleString() } {this.props.item.timestamp} </span>
                <button onClick={this.delete} >x</button>
            </div>
        );
    }
}

class ToDoForm extends Component {
    constructor (props) {
        super(props);
        this.save = this.save.bind(this);
        this.state = {valid: true};
    }

    validator(){
        return this.title.value && this.text.value;
    }

    save() {
        let valid = this.validator();
        this.setState({valid})
        if (valid){
            store.dispatch({type: 'NEW_TODO',
                            title:  this.title.value,
                            text:   this.text.value})
            this.title.value = '';
            this.text.value  = '';
        }
    }

    
    render (){
        let style = {
            backgroundColor: this.state.valid ? '' : 'red'
        }
        return (
            <div>
                <input style={style} placeholder='title' ref={ c => this.title = c}/>
                <input style={style} placeholder='text' ref={ c => this.text = c} />
                <button onClick = { this.save } >Save</button>
            </div>
        );
    }
}

class ToDoList extends Component {
    render (){
        return (
            <div> <h1>TODO LIST</h1>
                <ToDoForm />
                { this.props.items.map( (item, index) => <ToDoItem key={index} item={item} />) }
            </div>
        );
    }
}

const mapStateToProps = function(store){
    return {
        items: store.todo.items
    };
}

ToDoList = connect(mapStateToProps)(ToDoList);



class App extends Component {
  render() {
    return (
      <div className="App">
        <Provider store={store} >
            <ToDoList />
        </Provider>
      </div>
    );
  }
}

export default App;