Develop Reference

Why checkboxes dont change from checked to unchecked on click?

My React App doesn't work like it should be. The problem is that the checkboxes dont change at all.
I managed to show the checked boxes (the ones with the property of completed=true) and debugging it seems that it works fine when I click but for some reason the box that needs to be changed automatically re-changes on its own.
Do you have any idea why ?
//APP.JS
import React from "react"
import './App.css';
import Header from "./Header"
import TodoItem from "./todoItem";
import todosData from "./todosData"
class App extends React.Component {
constructor() {
super()
this.state = {
todos: todosData
}
this.handleChange = this.handleChange.bind(this)
}
handleChange(id) {
this.setState((prevState) => {
const newArray = prevState.todos.map((elem) => {
if(elem.id === id) {
elem.completed = !(elem.completed)
}
return elem
})
return {
todos: newArray
}
})
}
render() {
const todosArray = this.state.todos.map(item =>
<TodoItem
key={item.id}
item={item}
handleChange={this.handleChange}
/>)
return (
<div className="App">
<Header />
<div className="container">
{todosArray}
</div>
</div>
)
}
}
export default App;
//TODOITEM.JS
import React from "react"
function TodoItem(props) {
return (
<div className="elem-container">
<input type="checkbox"
checked={props.item.completed}
onChange={() => props.handleChange(props.item.id)}
/>
<span className="span-container">{props.item.text}</span>
</div>
)
}
export default TodoItem
//TODOSDATA.JS
const todosData = [
{
id: 1,
text: "Take out the trash",
completed: true
},
{
id: 2,
text: "Grocery shopping",
completed: false
},
{
id: 3,
text: "Clean gecko tank",
completed: false
},
{
id: 4,
text: "Mow lawn",
completed: true
},
{
id: 5,
text: "Catch up on Arrested Development",
completed: false
}
]
export default todosData
Thank you for the help in advance

you need to change two things and it will work just fine
first:
inside todoItem.js
onChange={(e) => props.handleChange(e,props.item.id)}
second:
inside the parent file
handleChange(event, id) {
this.setState((prevState) => {
const newArray = prevState.todos.map((elem) => {
if(elem.id === id) {
elem.completed = event.target.checked
}
return elem
})
return {
todos: newArray
}
})
}
now everything will work as you expected
have a nice day

I'm no expert as I'm learning React myself but looking at the code handleChange(id) doesn't have an else state in its 'if' statement, have you tried adding?

Adding to #mouheb answer, you can simplify one more step. you don't need to map the all elements to update single item. you can change directly item (if it is mutable).
// todoItem.js
onChange={(e) => props.handleChange(e, props.item) }
// parent file
handleChange(event, prop) {
prop.completed = event.target.
this.setState({ todos: this.state.todos }) or this.setState({ todos: [...this.state.todos] })
}

Checking the checkbox is not working in React

This is a simple TO-DO app in react in which App.js takes data from TodosData.js and the list is shown with the component TodoItem.js. Now the checkboxes and data can be viewed when rendered. But when I click on the checkbox it doesn't work. I tried console logging handleChange function which seems to work. It seems like there maybe problems inside the handleChange function which I can't figure out.
I am following a freecodecamp tutorial on YT and I also checked it several times but can't find the problem here.
App.js code:
import React from 'react';
import TodoItem from './TodoItem'
import todosData from './todosData'
class App extends React.Component {
constructor() {
super ()
this.state = { todos: todosData }
this.handleChange = this.handleChange.bind(this)
}
handleChange(id) {
this.setState(prevState => {
const updatedTodos = prevState.todos.map(todo => {
if (todo.id === id) {
todo.completed = !todo.completed
}
return todo
})
return {
todos: updatedTodos
}
})
}
render() {
const todoItems = this.state.todos.map(itemEach => <TodoItem key = {itemEach.id} itemEach = {itemEach}
handleChange = {this.handleChange} />)
return (
<div className = "todo-list">
{todoItems}
</div>
)
}
}
export default App;
TodoItem.js code:
import React from 'react';
function TodoItem(props) {
return(
<div className = "todo-item">
<input type = "checkbox"
checked={props.itemEach.completed}
onChange={() => props.handleChange(props.itemEach.id)}
/>
<p>{props.itemEach.text}</p>
</div>
)
}
export default TodoItem
TodosData.js code:
const todosData = [
{
id: 1,
text: "Take out the trash",
completed: true
},
{
id: 2,
text: "Grocery shopping",
completed: false
},
{
id: 3,
text: "Clearn gecko tank",
completed: false
},
{
id: 4,
text: "Mow lawn",
completed: true
},
{
id: 5,
text: "Catch up on Arrested Development",
completed: false
}
]
export default todosData
Is there a better way to implement this? This way of doing checkbox seems quite complicated for a beginner like myself. Also how can I improve this code?

You are mutating the state in your handleChange function. Hence it gets the prevState twice. Once for the original previous state, next for the update that you make inside the handleChange.
You can probably lose the reference, by spreading the todo from state like this.
this.setState(prevState => {
const updatedTodos = prevState.todos.map(todo => {
const resTodo = { ...todo };
if (todo.id === id) {
resTodo.completed = !resTodo.completed;
}
return resTodo;
});
return {
todos: updatedTodos
};
});
Here's a working codesandbox

is there any solution for my react state problem?

So I am a beginner in react. I was messing around with a to-do list and encountered a state related problem.
//main todolist
import React from 'react'
import './todolist.css'
import Itemtodo from './Itemtodo'
class Todolist extends React.Component{
constructor(){
super()
this.state = {
todos: [
{
id:1,
text: 'html',
completed: true
},
{
id:2,
text: 'css',
completed: true
},
{
id:3,
text: 'js',
completed: false
},
{
id:4,
text: 'react',
completed: false
},
{
id:5,
text: 'review',
completed: false
}
]
}
}
// i think it came from this method
ev = (id) =>{
this.setState((prev) =>{
const newarr = prev.todos.map((data) =>{
if(data.id === id){
data.completed = !data.completed
}
return data
})
return {
todos:newarr
}
})
}
render(){
const array = this.state.todos.map(data => <Itemtodo key={data.id} todo={data.text} ic={data.completed} ev={this.ev} id={data.id}/>)
return (
<div className="todolist">
{array}
</div>
)
}
}
export default Todolist
// item todo
import React, { Component } from 'react'
import './itemtodo.css'
export class Itemtodo extends Component {
render() {
return (
<div className ='itemtodo'>
<input type='checkbox' checked={this.props.ic} onChange={() => this.props.ev(this.props.id)}/>
<p>{this.props.todo}</p>
</div>
)
}
}
export default Itemtodo
I REALLY think that the problem was from "main todolist" because if I changed the "ev" method to do "checked every checkbox with a click" like this, it worked
// i think it came from this method
ev = (id) =>{
this.setState((prev) =>{
const newarr = prev.todos.map((data) =>{
data.completed = true
return data
})
return {
todos:newarr
}
}) //set state ends
}
I did some experiment by console loging the "newar" and it did not change. So I think it's because of the
data.completed = !data.completed
did not work please help me! Thank you

Hi Please check this example. It is working fine.
Todolist Component
import React, {Component} from 'react'
class Todolist extends React.Component {
constructor(props) {
super(props);
this.state = {
todos: [
{id: 1, text: 'html', completed: true},
{id: 2, text: 'css', completed: true},
{id: 3, text: 'js', completed: false},
{id: 4, text: 'react', completed: false},
{id: 5, text: 'review', completed: false}
]
}
}
// i think it came from this method
ev = (id, changedValue) => {
this.setState((prev) => {
let item = prev.todos.filter((data) => data.id === id)[0];
item.completed = changedValue;
return{
todos: prev.todos
};
})
};
render() {
const array = this.state.todos.map(data => <Itemtodo key={data.id} todo={data.text} ic={data.completed}
ev={this.ev} id={data.id}/>);
return (
<div className="todolist">
{array}
</div>
)
}
}
export default Todolist
Itemtodo Component
class Itemtodo extends Component {
render() {
return (
<div className='itemtodo'>
<input type='checkbox' checked={this.props.ic} onChange={() => this.props.ev(this.props.id, !this.props.ic)}/>
{this.props.todo}
</div>
)
}
}

Here is a working example of a todo list that has TodoItem as a pure component, because toggleCompleted will not mutate this will work (you have to click on the todo to toggle completed).
//using React.memo will make TodoItem a pure
// component and won't re render if props didn't change
const TodoItem = React.memo(function TodoItem({
todo: { id, name, completed },
toggleCompleted,
}) {
const r = React.useRef(0);
r.current++;
return (
<li
onClick={toggleCompleted(id)}
style={{ cursor: 'pointer' }}
>
rendered:{r.current}, {name}, completed:
{completed.toString()}
</li>
);
});
function TodoList({ todos, toggleCompleted }) {
return (
<ul>
{todos.map((todo) => (
<TodoItem
key={todo.id}
todo={todo}
toggleCompleted={toggleCompleted}
/>
))}
</ul>
);
}
function App() {
const [todos, setTodos] = React.useState([
{ id: 1, name: '1', completed: false },
{ id: 2, name: '2', completed: false },
]);
//use callback so the handler never changes
const toggleCompleted = React.useCallback(
(id) => () =>
setTodos((todos) =>
//map todos into a new array of todos
todos.map(
(todo) =>
todo.id === id
? //shallow copy todo and toggle completed
{ ...todo, completed: !todo.completed }
: todo //just return the todo
)
),
[]
);
return (
<TodoList
todos={todos}
toggleCompleted={toggleCompleted}
/>
);
}
ReactDOM.render(<App />, document.getElementById('root'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.4/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.4/umd/react-dom.production.min.js"></script>
<div id="root"></div>
And here is a broken example where I will mutate the todo, even though you changed the data you did not change the reference of the todo item so React won't re render pure TodoItem component.
//using React.memo will make TodoItem a pure
// component and won't re render if props didn't change
const TodoItem = React.memo(function TodoItem({
todo: { id, name, completed },
toggleCompleted,
}) {
const r = React.useRef(0);
r.current++;
return (
<li
onClick={toggleCompleted(id)}
style={{ cursor: 'pointer' }}
>
rendered:{r.current}, {name}, completed:
{completed.toString()}
</li>
);
});
function TodoList({ todos, toggleCompleted }) {
return (
<ul>
{todos.map((todo) => (
<TodoItem
key={todo.id}
todo={todo}
toggleCompleted={toggleCompleted}
/>
))}
</ul>
);
}
function App() {
const [todos, setTodos] = React.useState([
{ id: 1, name: '1', completed: false },
{ id: 2, name: '2', completed: false },
]);
//use callback so the handler never changes
const toggleCompleted = React.useCallback(
(id) => () =>
setTodos((todos) =>
//map todos into a new array of todos
todos.map((todo) => {
if (todo.id === id) {
todo.completed = !todo.completed;
console.log('changed todo:', todo);
}
//it is always returning the same todo that it
// got passed into, only mutates the one that
// needs to be toggled but that todo is still the
// same
return todo;
})
),
[]
);
return (
<TodoList
todos={todos}
toggleCompleted={toggleCompleted}
/>
);
}
ReactDOM.render(<App />, document.getElementById('root'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.4/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.4/umd/react-dom.production.min.js"></script>
<div id="root"></div>

Adding clicked items to new array in React

I am making API calls and rendering different components within an object. One of those is illustrated below:
class Bases extends Component {
constructor() {
super();
this.state = {
'basesObject': {}
}
}
componentDidMount() {
this.getBases();
}
getBases() {
fetch('http://localhost:4000/cupcakes/bases')
.then(results => results.json())
.then(results => this.setState({'basesObject': results}))
}
render() {
let {basesObject} = this.state;
let {bases} = basesObject;
console.log(bases);
//FALSY values: undefined, null, NaN, 0, false, ""
return (
<div>
{bases && bases.map(item =>
<button key={item.key} className="boxes">
{/* <p>{item.key}</p> */}
<p>{item.name}</p>
<p>${item.price}.00</p>
{/* <p>{item.ingredients}</p> */}
</button>
)}
</div>
)
}
}
The above renders a set of buttons. All my components look basically the same.
I render my components here:
class App extends Component {
state = {
ordersArray: []
}
render() {
return (
<div>
<h1>Bases</h1>
<Bases />
<h1>Frostings</h1>
<Frostings />
<h1>Toppings</h1>
<Toppings />
</div>
);
}
}
I need to figure out the simplest way to, when a button is clicked by the user, add the key of each clicked element to a new array and I am not sure where to start. The user must select one of each, but is allowed to select as many toppings as they want.

Try this
We can use the same component for all categories. All the data is handled by the parent (stateless component).
function Buttons({ list, handleClick }) {
return (
<div>
{list.map(({ key, name, price, isSelected }) => (
<button
className={isSelected ? "active" : ""}
key={key}
onClick={() => handleClick(key)}
>
<span>{name}</span>
<span>${price}</span>
</button>
))}
</div>
);
}
Fetch data in App component, pass the data and handleClick method into Buttons.
class App extends Component {
state = {
basesArray: [],
toppingsArray: []
};
componentDidMount() {
// Get bases and toppings list, and add isSelected attribute with default value false
this.setState({
basesArray: [
{ key: "bases1", name: "bases1", price: 1, isSelected: false },
{ key: "bases2", name: "bases2", price: 2, isSelected: false },
{ key: "bases3", name: "bases3", price: 3, isSelected: false }
],
toppingsArray: [
{ key: "topping1", name: "topping1", price: 1, isSelected: false },
{ key: "topping2", name: "topping2", price: 2, isSelected: false },
{ key: "topping3", name: "topping3", price: 3, isSelected: false }
]
});
}
// for single selected category
handleSingleSelected = type => key => {
this.setState(state => ({
[type]: state[type].map(item => ({
...item,
isSelected: item.key === key
}))
}));
};
// for multiple selected category
handleMultiSelected = type => key => {
this.setState(state => ({
[type]: state[type].map(item => {
if (item.key === key) {
return {
...item,
isSelected: !item.isSelected
};
}
return item;
})
}));
};
// get final selected item
handleSubmit = () => {
const { basesArray, toppingsArray } = this.state;
const selectedBases = basesArray.filter(({ isSelected }) => isSelected);
const selectedToppings = toppingsArray.filter(({ isSelected }) => isSelected);
// submit the result here
}
render() {
const { basesArray, toppingsArray } = this.state;
return (
<div>
<h1>Bases</h1>
<Buttons
list={basesArray}
handleClick={this.handleSingleSelected("basesArray")}
/>
<h1>Toppings</h1>
<Buttons
list={toppingsArray}
handleClick={this.handleMultiSelected("toppingsArray")}
/>
</div>
);
}
}
export default App;
CSS
button {
margin: 5px;
}
button.active {
background: lightblue;
}

I think the following example would be a good start for your case.
Define a handleClick function where you can set state with setState as the following:
handleClick(item) {
this.setState(prevState => {
return {
...prevState,
clickedItems: [...prevState.clickedItems, item.key]
};
});
}
Create an array called clickedItems in constructor for state and bind handleClick:
constructor() {
super();
this.state = {
basesObject: {},
clickedItems: [],
}
this.handleClick = this.handleClick.bind(this);
}
You need to add a onClick={() => handleClick(item)} handler for onClick:
<button key={item.key} className="boxes" onClick={() => handleClick(item)}>
{/* <p>{item.key}</p> */}
<p>{item.name}</p>
<p>${item.price}.00</p>
{/* <p>{item.ingredients}</p> */}
</button>
I hope that helps!

Checkbox does not want to check or uncheck after clicking

Iterates on the todos array. Objects inside have the isChecked property. If isChecked === true marks the checkbox, ifisChecked === false the checkbox is uncheckbox. When I click on the checkbox. I can't mark or uncheckbox
Demo here: https://stackblitz.com/edit/react-ds9rsd
class App extends Component {
constructor() {
super();
this.state = {
todos: [
{
name:'A',
id: 1,
isChecked: true
},
{
name:'B',
id: 2,
isChecked: false
},
{
name:'C',
id: 3,
isChecked: true
}
]
};
}
checked = (e) => {
console.log(e.target.checked)
}
render() {
return (
<div>
{this.state.todos.map((todo, index) => {
return <input type="checkbox" checked={todo.isChecked} onChange={(e) => this.checked(e)}/>
})}
</div>
);
}
}

In checked() function you are just logging the value. Instead of that you need to do setState() to save new state.

A possibile solution could be updating the render function like this:
render() {
return (
<div>
{this.state.todos.map((todo, index) => {
return <input label={todo.name} type="checkbox" checked={todo.isChecked}
onChange={(e) => this.checked(todo)}/>
})}
</div>
);
}
and the checked method like this:
checked = (e) => {
this.setState(state => {
const list = state.todos.map((item) => {
if (item.name === e.name) {
return item.isChecked = !item.isChecked;
} else {
return item;
}
});
return {
list,
};
});
}

You will need to add a function and call it for each checkbox
import React, { Component } from "react";
import { render } from "react-dom";
import Hello from "./Hello";
import "./style.css";
class App extends Component {
constructor() {
super();
this.state = {
todos: [
{
name: "A",
id: 1,
isChecked: true
},
{
name: "B",
id: 2,
isChecked: false
},
{
name: "C",
id: 3,
isChecked: true
}
]
};
}
checked = index => {
/** get the current state */
let _todos = this.state.todos;
/** assign opposite value: true to false or false to true */
_todos[index].isChecked = !_todos[index].isChecked;
/** update state */
this.setState({ todos: _todos });
};
render() {
return (
<div>
{this.state.todos.map((todo, index) => {
/** call the function passing the index value */
return (
<input
label={todo.name}
type="checkbox"
checked={todo.isChecked}
onChange={this.checked.bind(this, index)}
/>
);
})}
</div>
);
}
}
render(<App />, document.getElementById("root"));