Try to check the checkbox, you will see undefined. That's strange I think I used find properly. Or there's a better way to do it?
http://jsbin.com/ficijuwexa/1/edit?js,console,output
class HelloWorldComponent extends React.Component {
constructor(){
super()
this.handleChange = this.handleChange.bind(this);
this.state = {
"fruits":[
{"name":"banana","value":true},
{"name":"watermelon","value":false},
{"name":"lemon","value":true},
]
}
}
handleChange(e,key){
const newFruitsData = this.state.fruits.find(obj => {
obj.name === key ? obj.value = e.target.checked : ''
});
console.log(newFruitsData) // <-- why does this output undefined?
}
render() {
return (
<div>
{this.state.fruits.map(obj =>
<div key={obj.name}>
<label>{obj.name}</label>
<input onChange={(e) => this.handleChange(e, obj.name)} type="checkbox" defaultChecked={obj.value} />
</div>
)}
<br />
<pre>{JSON.stringify(this.state.fruits,null,2)}</pre>
</div>
);
}
}
Your find has no return statement, it always return undefined while it should return boolean
const newFruitsData = this.state.fruits.find(obj => obj.name === key && obj.value === e.target.checked);
In the handleChange(), the Array.prototype.find should return Bool:
handleChange(e,key){
let nxState = Object.assign({}, this.state)
nxState.fruits.find(obj => {
if (obj.name === key) {
obj.value = e.target.checked
return true
} else {
return false
}
});
this.setState(nxState)
}
And you should use setState() instead, it's my opinion of course
--- Update
Check it
Related
I'd like to store todo data with localStorage so that it won't disappear after refreshing the page.
I used React class component when started creating.
I've added 'handleFormSubmit' and 'ComponentDidMount' methods.
nothing stores in localStorage when I type todo and choose date.
get an error in ComponentDidMount with
Line 'const result = localData ? JSON.parse(localData) : [];'
:SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data
how can I set and get items?
It would be really appreciated if I could get help.
I'd like to make this app really work.
import React from "react"
import TodoItem from "./components/TodoItem"
import todosData from "./components/todosData"
class App extends React.Component {
constructor(props) {
super(props)
this.state = {
todos: todosData,
//setTodos: todosData,
newItem: "",
deadline: "",
editing: false
}
this.handleChange = this.handleChange.bind(this)
this.addTodo = this.addTodo.bind(this)
this.updateInput = this.updateInput.bind(this)
this.deleteItem = this.deleteItem.bind(this)
this.updateItem = this.updateItem.bind(this)
this.updateDeadline = this.updateDeadline.bind(this)
this.updateInputDeadline = this.updateInputDeadline.bind(this)
this.editItem = this.editItem.bind(this)
this.handleFormSubmit = this.handleFormSubmit.bind(this)
}
handleChange(id) {
this.setState((prevState) => {
const updatedTodos = prevState.todos.map((todo) => {
if (todo.id === id) {
return { ...todo, completed: !todo.completed };
} else {
return todo;
}
});
return { todos: updatedTodos };
});
}
addTodo(e) {
e.preventDefault();
const newTodo = {
id: this.state.todos.length + 1,
text: this.state.newItem,
completed: false,
deadline: this.state.deadline
}
const newTodos = this.state.todos.concat([newTodo]);
this.setState({
todos: newTodos
})
}
updateInput(value, id) {
this.setState((prevState) => {
const updatedTodos = prevState.todos.map((todo) => {
if(todo.id === id) {
return {...todo, text: value}
}else {
return todo;
}
})
return {todos: updatedTodos}
})
}
updateInputDeadline(value, id) {
this.setState((prevState) => {
const updatedTodos = prevState.todos.map((todo) => {
if(todo.id === id) {
console.log(value, id);
return {...todo, deadline: value}
}else {
return todo;
}
})
return {todos: updatedTodos}
})
}
updateItem(e) {
this.setState({
newItem: e.target.value
})
}
updateDeadline(e) {
this.setState({
deadline: e.target.value
})
}
deleteItem(id){
const filteredItems= this.state.todos.filter(item =>
item.id!==id);
this.setState({
todos: filteredItems
})
}
editItem(id) {
this.setState({
editing: id
})
}
handleFormSubmit() {
const { todo, deadline } = this.state;
localStorage.setItem('todo', JSON.stringify(todo));
localStorage.setItem('deadline', deadline);
};
componentDidMount() {
const localData = localStorage.getItem('todo');
const result = localData ? JSON.parse(localData) : [];
const deadlineData = localStorage.getItem('deadline');
this.setState({ result, deadlineData });
}
render() {
const todoItems = this.state.todos.map
(item =>
<TodoItem
key={item.id}
item={item}
handleChange={this.handleChange}
addTodo={this.addTodo}
deleteItem={this.deleteItem}
updateInput={this.updateInput}
updateInputDeadline={this.updateInputDeadline}
isEdited={this.state.editing === item.id}
editItem={this.editItem}
/>)
return (
<div className="todo-list">
<Timer />
<form onSubmit={this.handleFormSubmit}>
<div className="add-todo">
<label>Add an item...</label>
<input
type="text"
name="todo"
placeholder="Type item here..."
value={this.state.newItem}
onChange={this.updateItem}
/>
</div>
<div className="date">
<label htmlFor="deadline">Deadline</label>
<input
type="date" id="start" name="deadline"
min="2021-01-01"
max="2024-12-31"
value={this.state.deadline}
onChange={this.updateDeadline}
/>
</div>
<button type="submit" onClick={this.addTodo}>Add to the list</button>
</form>
{todoItems.length === 0 ? <p>No items</p> : null}
<div className="todoitems">
{todoItems}
</div>
</div>
)
}
}
export default App
When you press the button, there are two events that you are trying to call - addTodo and handleFormSubmit. Since you are calling e.preventDefault() in addTodo, the submit event is never called. You could do all of the actions you need in one of the methods.
My guess is that you are either trying to JSON.parse an array instead of an object, or the value of todo is undefined. You are trying to get todo out of this.state, but you only have todos in your state, so it might be a typo. The same goes for deadline.
You are doing the setting and getting correctly. You could actually get data from localStorage even when you are first setting the state in constructor. But the componendDidMount approach you tried is also good.
constructor(props) {
super(props)
const cachedTodos = localStorage.getItem("todo")
this.state = {
todos: cachedTodos ?? todosData,
...
}
In the output, Only the default completed values are checked! not able change the checks of tasks.
These are my Java script files
app.js
class App extends Component {
constructor() {
super()
this.state = {
todos: Todosdata
}
this.handleChange = this.handleChange.bind(this)
}
handleChange(id) {
this.setState(prevState => {
const udpated = prevState.todos.map(todo => {
if (todo.id === id) {
todo.completed = !todo.completed
}
return todo
})
return {
todos: udpated
}
})
}
render() {
const todoelements = this.state.todos.map(item => <ToDoItem key={item.id}
todoitem={item}
handleChange={this.handleChange} />)
return (
<div className="App">
< div className="todo-list" >
{todoelements}
</div >
</div>
)
}
}
ToDoItem.js
const ToDoItem = (props) => {
const Afterstyle = {
fontColor: "red",
textDecoration: "line-through"
}
return (
<div className="todo-item">
<input type="checkbox"
checked ={props.todoitem.completed}
onChange ={() => props.handleChange(props.todoitem.id)} />
<p style={props.todoitem.completed ? Afterstyle : null}>{props.todoitem.task}</p>
</div>
)
}
i did console log inside if condition of handle Change method,its printing 2 times.
I am stuck at this for hours please fix this!
You are mutating the todo item instead of creating a new one. Change your handler like that:
handleChange(id) {
this.setState(prevState => {
const udpated = prevState.todos.map(todo => {
if (todo.id === id) {
// if the id matches return a new object
return {...todo, completed: !todo.completed};
}
return todo
});
return {todos: udpated};
}
}
Live Demo:
I want to check the values of this.state.cityCodeval and this.state.idVal using an if statement inside the displayName() method so it can display what's inside the return() if the values inputted by the user are correct.
In my Webstorm IDE, I get a warning that says:
Binary operation argument type string is not compatible with type string
Which makes me believe I'm checking for their values the wrong way.
I know I could just do console.log(this.state.cityCodeval); or console.log(this.state.idVal);, but I need to check for what the user input is.
Here's my code
import React, { Component } from 'react';
import { connect } from 'react-redux';
import * as actionType from '../../store/actions/actions';
class SearchArticle extends Component {
constructor(props) {
super(props);
this.state = {
flag: false,
idVal: '',
cityCodeval: ''
};
this.handleChange = this.handleChange.bind(this);
this.handleArticleId = this.handleArticleId.bind(this);
this.handleSubmit = this.handleSubmit.bind(this);
}
handleSubmit(event) {
event.preventDefault();
console.log("IDValue --> " + this.state.idVal);
this.props.articleIdValueRedux(this.state.idVal);
this.setState({flag: true});
}
handleChange = event => {
this.setState({value: event.target.value});
this.props.cityCodeReducerRedux(event.target.value);
}
handleArticleId = event => {
event.preventDefault();
this.setState({idVal: event.target.value});
}
displayName = () => {
if(this.state.cityCodeval === 'nyc' && this.state.idVal === '1') {
return (
<div>
<p>author name: {this.state.authorNameValue}</p>
<p>article text: {this.state.storyTextValue}</p>
</div>
);
}
}
render() {
return(
<div>
<form onSubmit={this.handleSubmit}>
<input onChange={this.handleChange} value={this.state.cityCodeValue} type="text" placeholder="city code"/>
<input onChange={this.handleArticleId} value={this.state.idVal} placeholder="article id"/>
<button type="submit" value="Search">Submit</button>
{this.state.flag ? this.displayName() : null}
</form>
</div>
);
}
}
const mapStateToProps = state => {
return {
cityCodeValue: state.cityCodeValue.cityCodeValue,
authorNameValue: state.authorNameValue.authorNameValue,
articleIdValue: state.articleIdValue.articleIdValue,
storyTextValue: state.storyTextValue.storyTextValue
};
};
const mapDispatchToProps = dispatch => {
return {
cityCodeReducerRedux: (value) => dispatch({type: actionType.CITY_CODE_VALUE, value}),
articleIdValueRedux: (value) => dispatch({type: actionType.ARTICLE_ID_VALUE, value})
};
};
export default connect(mapStateToProps, mapDispatchToProps)(SearchArticle);
You should still return null; as a safe clause just in case your condition doesn't match.
displayName = () => {
if(this.state.cityCodeval === 'nyc' && this.state.idVal === '1') {
console.log(this.state.cityCodeval); // console it here
console.log(this.state.idVal); // console it here
return (
<div>
<p>author name: {this.state.authorNameValue}</p>
<p>article text: {this.state.storyTextValue}</p>
</div>
);
}
return null;
}
Also now, in your render method you can do this.
{this.state.flag && this.displayName()}
This means that if the flag variable is true, call displayName it then executes the function. If you first condition matches it will return that otherwise it will return null;
Previously in your current code if the flag variable was true and it executed the function displayName where the if condition didn't meet. This caused an error because it had nothing to return.
I need your fresh eyes to help me.
I have a set of answers in my array which I shuffle on the first render.
My problem here, is that I know if i am clicking on one of the answer, the setState will re-render and consequently re-shuffle my array which i dont want.
You can have a look at my code below:
export default class extends React.Component {
constructor(props) {
super(props)
this.state = {
user: this.props.user,
token: this.props.token,
data: this.props.data,
count: 0,
select: undefined
}
this.changeQuestion = this.changeQuestion.bind(this);
this.onCorrect = this.onCorrect.bind(this);
this.onFalse = this.onFalse.bind(this);
}
static async getInitialProps({req, query}) {
const id = query.id;
const authProps = await getAuthProps(req, 'Country/Questions?theory=' + id)
return authProps
}
componentDidMount() {
if (this.state.user === undefined) {
Router.push('/login')
}
}
changeQuestion() {
this.setState({
count: this.state.count + 1,
select: undefined
})
}
onCorrect() {
this.setState({
select: true
})
}
onFalse() {
this.setState({
select: true
})
}
mixAnswers() {
const answer = this.props.data.Properties.Elements
const answers = answer[this.state.count].Properties.Answers
const answersObj = answers.reduce((ac, el, i) => {
ac.push(
<p key={i} onClick={i === 0
? this.onCorrect
: this.onFalse} className={i === 0
? 'exercices__answers--correct'
: 'exercices__answers--false'}>{el}</p>
)
return ac
}, [])
const answersShuffled = answersObj.sort(() => 0.5 - Math.random())
return answersShuffled;
}
render() {
const {user, token, data} = this.state
const answer = this.props.data.Properties.Elements
const answers = answer[this.state.count].Properties.Answers
return (
<div>
{user !== undefined
? <Layout user={this.state.user}>
<div>
{answer[this.state.count].Properties.Sources !== undefined
? <img src={answer[this.state.count].Properties.Sources[0].URL}/>
: ''}
<h1>{answer[this.state.count].Properties.Question}</h1>
{this.mixAnswers().map((el, i) => <p key={i} onClick={el.props.onClick} className={this.state.select !== undefined
? el.props.className
: ''}>{el.props.children}</p>)
}
<p>{answer[this.state.count].Properties.Description}</p>
</div>
<button onClick={this.changeQuestion}>Next Question</button>
</Layout>
: <h1>Loading...</h1>}
</div>
)
}
}
Obviously, the way I am using the 'this.mixAnswers()' method is the issue. How can I prevent it to re-render then re-shuffle this array of questions.
PS: dont pay attention about onCorrect() and onFalse().
You should make sure the logic that shuffle the answers is called only once, you can get this behavior on ComponentWillMount or ComponentDidMount, then you save them in the state of the component and in the render function instead of
{this.mixAnswers().map((el, i) => <p key={i} onClick={el.props.onClick} className={this.state.select !== undefined
? el.props.className
: ''}>{el.props.children}</p>)
}
You use this.state.answers.map()...
How do I render an indeterminate checkbox via JSX?
Here's what I've tried:
function ICB({what}) {
return <input type="checkbox"
checked={what === "checked"}
indeterminate={what === "indeterminate"} />;
}
However, indeterminate is not an attribute on the HTMLElement, but a property. How do I set properties from React / JSX?
Solution:
As most of the answers below use findDOMNode or string refs, both of which are no longer considered good practice in React, I've written a more modern implementation:
function ICB() {
const [state, setState] = React.useState(0);
const indetSetter = React.useCallback(el => {
if (el && state === 2) {
el.indeterminate = true;
}
}, [state]);
const advance = () => setState(prev => (prev + 1) % 3);
return <input type="checkbox"
checked={state === 1}
ref={indetSetter}
onClick={advance} />;
}
ReactDOM.render(<ICB />, document.getElementById("out"));
<div id="out"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.13.1/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.13.1/umd/react-dom.production.min.js"></script>
You can also use the ref function directly:
ReactDOM.render(
<label>
<input
type="checkbox"
ref={input => {
if (input) {
input.indeterminate = true;
}
}}
/>
{' '}
Un test
</label>,
document.getElementById('root')
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="root"></div>
I would probably create a composite component that encapsulates the necessary hooks to set or unset the checkbox's indeterminate property. It looks like you're using ES2015 syntax, so I'll use some of those features here.
class IndeterminateCheckbox extends React.Component {
componentDidMount() {
if (this.props.indeterminate === true) {
this._setIndeterminate(true);
}
}
componentDidUpdate(previousProps) {
if (previousProps.indeterminate !== this.props.indeterminate) {
this._setIndeterminate(this.props.indeterminate);
}
}
_setIndeterminate(indeterminate) {
const node = React.findDOMNode(this);
node.indeterminate = indeterminate;
}
render() {
const { indeterminate, type, ...props } = this.props;
return <input type="checkbox" {...props} />;
}
}
// elsewhere
render() {
return <IndeterminateCheckbox
checked={this.props.state === "checked"}
indeterminate={this.props.state === "indeterminate"} />
}
Working example: https://jsbin.com/hudemu/edit?js,output
You can use the componentDidMount step (which is invoked after the initial rendering) to set that property:
componentDidMount() {
React.findDOMNode(this).indeterminate = this.props.state === "indeterminate";
}
If you want that property to be updated with subsequent renders, do the same thing in componentDidUpdate also.
I'd suggest creating a simple component (code ported from coffeescript so mind you, might have some simple typos):
const React = require('react');
module.exports = class IndeterminateCheckbox extends React.Component {
componentDidMount() {
this.refs.box.indeterminate = this.props.indeterminate;
}
componentDidUpdate(prevProps, prevState) {
if(prevProps.indeterminate !== this.props.indeterminate) {
this.refs.box.indeterminate = this.props.indeterminate;
}
}
render() {
return <input {...this.props} ref="box" type="checkbox"/>;
}
}
Now you have a simple component that behaves exactly like a checkbox, that supports the indeterminate prop. Note there's plenty of room for improvements here, namely setting propTypes and proper defaults for some props, and of course implementing componentShouldUpdate to only do something when needed.
An alternative would be to use a ref attribute with a callback to set the property on the DOM node. For example:
render: function() {
return (
<input
type="checkbox"
ref={function(input) {
if (input != null) {
React.findDOMNode(input).indeterminate = this.props.indeterminate;
}}
{...this.props} />
)
}
Dont use React.findDOMNode(this).
It is risky.
export class SelectAll extends Component {
constructor(props) {
super(props);
this.state = {
checked: false
};
this.myRef = React.createRef();
this.onChange = this.onChange.bind(this);
this.update = this.update.bind(this);
}
onChange(e) {
const checked = e.target.checked;
this.setState({
checked: checked
});
this.selectAllNode.indeterminate = false;
}
update(state: {
checked: Boolean,
indeterminate: Boolean
}) {
this.setState({
checked: state.checked
});
this.myRef.current.indeterminate = state.indeterminate;
}
render() {
return ( <
input type = "checkbox"
name = "selectAll"
checked = {
this.state.checked
}
onChange = {
this.onChange
}
ref = {
this.myRef
}
/>
);
}
}
React v15 implementation:
import React from 'react';
export default class Checkbox extends React.Component {
componentDidMount() {
this.el.indeterminate = this.props.indeterminate;
}
componentDidUpdate(prevProps, prevState) {
if(prevProps.indeterminate !== this.props.indeterminate) {
this.el.indeterminate = this.props.indeterminate;
}
}
render() {
const {indeterminate, ...attrs} = this.props;
return <input ref={el => {this.el = el}} type="checkbox" {...attrs}/>;
}
}
Taken from my tutorial which shows how this works with the recent React features. I hope this helps someone who stumbles upon this older question:
const App = () => {
const [checked, setChecked] = React.useState(CHECKBOX_STATES.Empty);
const handleChange = () => {
let updatedChecked;
if (checked === CHECKBOX_STATES.Checked) {
updatedChecked = CHECKBOX_STATES.Empty;
} else if (checked === CHECKBOX_STATES.Empty) {
updatedChecked = CHECKBOX_STATES.Indeterminate;
} else if (checked === CHECKBOX_STATES.Indeterminate) {
updatedChecked = CHECKBOX_STATES.Checked;
}
setChecked(updatedChecked);
};
return (
<div>
<Checkbox
label="Value"
value={checked}
onChange={handleChange}
/>
<p>Is checked? {checked}</p>
</div>
);
};
const Checkbox = ({ label, value, onChange }) => {
const checkboxRef = React.useRef();
React.useEffect(() => {
if (value === CHECKBOX_STATES.Checked) {
checkboxRef.current.checked = true;
checkboxRef.current.indeterminate = false;
} else if (value === CHECKBOX_STATES.Empty) {
checkboxRef.current.checked = false;
checkboxRef.current.indeterminate = false;
} else if (value === CHECKBOX_STATES.Indeterminate) {
checkboxRef.current.checked = false;
checkboxRef.current.indeterminate = true;
}
}, [value]);
return (
<label>
<input ref={checkboxRef} type="checkbox" onChange={onChange} />
{label}
</label>
);
};