I have {onView: '0'} in the state goes down as props to my View component.
But the state {min: 0, max: 100} doesn't go down to my Range component.
Where did I go wrong?
App.js:
export class Generator extends React.Component {
constructor (props) {
super(props)
this.state = {
onView: '0',
min: 0,
max: 100
}
}
render() {
var btnClick = () => {
var x = Math.ceil(Math.ceil(Math.random()) / Math.random());
return this.setState({ onView : x });
};
return (
<div className="container">
<Instructions />
<Range max={this.state.max} min={this.state.min} />
<Generate currentClick={btnClick} />
<View show={this.state.onView} />
</div>
);
}
}
export default Generator;
View Component:
const View = ({ show }) => {
return (
<div className="view">
<h1>{show}</h1>
</div>
);
}
export default View;
Range component:
class Range extends React.Component {
constructor(props) {
super(props)
}
render() {
return (
<div className="rangeDiv">
<input type="text" value={this.min}/>
<input type="text" value={this.max}/>
</div>
);
}
}
export default Range;
I would appreciate any help here, thanks!
try this out please! I guess you missed the props there
<input type="text" value={this.props.min}/>
You are using this.min instead of this.props.min and the same for max.
Try this:
class Range extends React.Component {
constructor(props) {
super(props);
}
render() {
const { min, max } = this.props;
return (
<div className="rangeDiv">
<input type="text" value={min} />
<input type="text" value={max} />
</div>
);
}
}
export default Range;
Related
I am new to React and I am finding it difficult to pass props from one component to another.
This is the first component
export default class App extends React.Component {
constructor(props) {
super(props);
this.state = {
count: 0,
// show:true
};
}
counter = () => {
this.setState({ count: this.state.count + 1 });
};
render() {
return (
<div className="">
<div>{this.state.count}</div>
</div>
);
}
}
and this is the second
export default class Button extends React.Component {
render() {
return (
<div className="">
<App />
<button onClick={this.counter}>Click me</button>
</div>
);
}
}
How do I make the counter count by passing props in the apps component
export default class App extends React.Component {
constructor(props) {
super(props);
this.state = {
count: 0,
// show:true
};
}
counter = () => {
this.setState({ count: this.state.count + 1 });
};
render() {
return (
<div className="">
<div>{this.state.count}</div>
<Button counter={this.counter} />
</div>
);
}
}
export default class Button extends React.Component {
render() {
return (
<div className="">
<button onClick={this.props.counter}>Click me</button>
</div>
);
}
}
I have two child components. The first child is an image and the second child is a search input. When I type something in the input field, I want the image to hide itself. The passing of data from the second child to the parent goes well. But the first child still appears...
Parent:
class Main extends React.Component {
constructor() {
super();
this.state = {
displayValue: 'block'
};
}
hideImage = () => () => {
alert('You pressed a key, now the apple should be gone')
this.setState ({
displayValue: 'none'
});
};
render() {
return (
<div>
<Image />
<Search hideImage={this.hideImage()}/>
</div>
);
}
}
ReactDOM.render(<Main />, document.getElementById('root'));
First Child:
export default class Image extends Component {
render() {
return (
<div>
<img style={{display : this.props.displayValue}} src="https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcTAxoq2YSBjoS0Lo3-zfqghoyNzZ9jHxoOc5xuFBoopMtKP6n4B"></img>
</div>
)
}
}
Second Child:
export default class Search extends Component {
render() {
return (
<div>
<input onInput={this.props.hideImage} placeholder="Search someting"></input>
</div>
)
}
}
You have to pass the displayValue state into your Image component as a prop. Also you have to pass the hideImage function without initializing it using the two brackets. The below code should work for you.
class Main extends React.Component {
constructor() {
super();
this.state = {
displayValue: 'block'
};
}
hideImage = () => () => {
alert('You pressed a key, now the apple should be gone')
this.setState ({
displayValue: 'none'
});
};
render() {
return (
<div>
<Image displayValue={this.state.displayValue}/>
<Search hideImage={this.hideImage}/>
</div>
);
}
}
You just had a couple of typos.
class Image extends React.Component {
render() {
return (
<div>
<img
style={{ display: this.props.displayValue }}
src="https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcTAxoq2YSBjoS0Lo3-zfqghoyNzZ9jHxoOc5xuFBoopMtKP6n4B"
alt="altprop"
/>
</div>
);
}
}
// Second Child:
class Search extends React.Component {
render() {
return (
<div>
<input onInput={this.props.hideImage} placeholder="Search someting" />
</div>
);
}
}
class Main extends React.Component {
constructor() {
super();
this.state = {
displayValue: "block"
};
}
hideImage(e) {
e.preventDefault();
alert("You pressed a key, now the apple should be gone");
this.setState({
displayValue: "none"
});
};
render() {
return (
<div>
<Image displayValue={this.state.displayValue}/>
<Search hideImage={this.hideImage.bind(this)} />
</div>
);
}
}
Call your Image component like this
<Image displayValue={this.state.displayValue} />
It should then already work, but here is a shorter way to write your code.
// First Child:
const Image = ({displayValue}) => <div>
<img alt='' style={{display : displayValue}} src="https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcTAxoq2YSBjoS0Lo3-zfqghoyNzZ9jHxoOc5xuFBoopMtKP6n4B"></img>
</div>
When I insert any text in input field, screen disappears, I am new to UI, learning ReactJs, help me out please.
import React from 'react';
class InputChange extends React.Component{
constructor(props){
super(props)
this.state={
input:''
}
}
updateState = (text) => {
this.setState({input: text});
}
render(){
return(
<div>
<div>Input:{this.state.input}</div>
<div>
<input type="text" value={this.state.input} onChange={this.updateState} />
</div>
</div>`
);
}
}
export default InputChange;
It's event.target.value...:
class InputChange extends React.Component {
state = { input: '' };
updateState = event => {
this.setState({ input: event.target.value });
};
render() {
return (
<div>
<div>Input:{this.state.input}</div>
<div>
<input
type="text"
value={this.state.input}
onChange={this.updateState}
/>
</div>
</div>
);
}
}
export default InputChange;
More info in the docs: https://reactjs.org/docs/forms.html
I'm learning react, and I'm stuck with not updating list components.
The component shows all of the list elements that I add manually, but not rendering any changes.
I searched a lot for solutions.
All of my change handlers are binded, the setState inside handleSubmit should update ClockRow...
My App.js:
import React, { Component } from 'react';
import Clock from './Clock';
import ClockRow from './ClockRow';
class App extends Component {
constructor(props) {
super(props);
this.state = {items: [], tle: 'Teszt', ival: 200};
this.handleChangeTitle = this.handleChangeTitle.bind(this);
this.handleChangeInterval = this.handleChangeInterval.bind(this);
this.handleSubmit = this.handleSubmit.bind(this);
}
handleChangeTitle(event) {
this.setState({tle: event.target.value});
}
handleChangeInterval(event) {
this.setState({ival: event.target.value});
}
handleSubmit(event) {
if(this.state.tle.length > 0 && this.state.ival > 9){
this.setState({items: [...this.state.items, <Clock interval={this.state.ival} title={this.state.tle} />]});
}
event.preventDefault();
}
render(){
return (
<div>
<div className="row">
<h1 className="col text-center">Hello, React!</h1>
</div>
<div className="row">
<form onSubmit={this.handleSubmit}>
<label>
Title: <input type="text" name="tle" value={this.state.tle} onChange={this.handleChangeTitle} />
</label>
<label>
Interval: <input type="number" name="ival" value={this.state.ival} onChange={this.handleChangeInterval} />
</label>
<input type="submit" value="Add" />
</form>
</div>
<ClockRow clockItems={this.state.items} />
</div>
);
}
}
export default App;
My ClockRow.js:
import React, { Component } from 'react';
class ClockRow extends Component{
constructor(props){
super(props);
this.state = {clocks: props.clockItems.map((x, i) => <div className="col" key={i}>{x}</div>) }
}
render(){
return(<div className="row">{this.state.clocks}</div>
)};
}
export default ClockRow;
My Clock.js:
import React, { Component } from 'react';
import {Card, CardTitle, CardBody, CardFooter} from 'reactstrap';
class Clock extends Component {
constructor(props){
super(props);
this.state = {counter: 0, interval: parseInt(props.interval), title: props.title};
}
componentDidMount() {
this.timerID = setInterval(() => this.tick(), this.state.interval);
}
componentWillUnmount() {
clearInterval(this.timerID);
}
tick() {
this.setState((state) => ({
counter: state.counter + 1
}));
}
render() {
return (
<Card>
<CardTitle>{this.state.title}</CardTitle>
<CardBody>{this.state.counter}</CardBody>
<CardFooter>{this.state.interval}</CardFooter>
</Card>
);
}
}
export default Clock;
CodeSandbox:
https://codesandbox.io/s/zxlzzv05n3
ClockRow.js is surplus
Clock.js is not changed
App.js is changed, and "React styled":
import React, { Component } from "react";
import Clock from "./Clock";
class App extends Component {
constructor(props) {
super(props);
this.state = { items: [], inputTle: "Teszt", inputIval: 200 };
}
handleChangeTitle = event => {
this.setState({ inputTle: event.target.value });
};
handleChangeInterval = event => {
this.setState({ inputIval: event.target.value });
};
handleSubmit = event => {
console.log(this.state);
if (this.state.inputTle.length > 0 && this.state.inputIval > 9) {
this.setState(prevState => {
return {
items: [
...prevState.items,
{
title: this.state.inputTle,
interval: this.state.inputIval
}
]
};
});
}
event.preventDefault();
};
render() {
return (
<div>
<div className="row">
<h1 className="col text-center">Hello, React!</h1>
</div>
<div className="row">
<form onSubmit={this.handleSubmit}>
<label>
Title:{" "}
<input
type="text"
name="tle"
value={this.state.inputTle}
onChange={this.handleChangeTitle}
/>
</label>
<label>
Interval:{" "}
<input
type="number"
name="ival"
value={this.state.inputIval}
onChange={this.handleChangeInterval}
/>
</label>
<input type="submit" value="Add" />
</form>
</div>
<div className="row">
{this.state.items.map((item, index) => (
<div className="col" key={index}>
<Clock {...item} />
</div>
))}
</div>
</div>
);
}
}
export default App;
I have a constructor in my main component:
class App extends Component {
constructor(props){
super(props);
this.state = {
items: []
}
};
render() {
return (
<div className="App">
<ItemList items={this.state.items}/>
<AddItemForm items={this.state.items}/>
</div>
);
}
}
In component AddItemForm I'm adding to array items objects with properties "item_name" that is string and "comment" with data type object. View of component:
class AddItemForm extends React.Component {
constructor(props) {
super(props);
this.state = {
item:{}
};
this.handleChange = this.handleChange.bind(this);
this.handleSubmit = this.handleSubmit.bind(this);
}
handleChange(event) {
this.setState({item:
{
item_name: event.target.value,
comment:{}
}
});
}
handleSubmit(event) {
event.preventDefault();
this.props.items.push(this.state.item);
}
render() {
return (
<form onSubmit={this.handleSubmit}>
<label>
<input type="text" item_name={this.state.value} onChange={this.handleChange} />
</label>
<input type="submit" value="Submit" />
</form>
);
}
}
export default AddItemForm;
How can I iterate this array to get all item_name values of every object and display them as list in my ItemList component?
This should help.
class App extends Component {
constructor(props){
super(props);
this.state = {
items: []
}
};
addItemToItemsList = (item) => {
const {items=[]} = this.state;
items.push(item);
this.setState({
items : items
});
}
render() {
return (
<div className="App">
<ItemList items={this.state.items}/>
<AddItemForm
items={this.state.items}
addItemToItemsList={this.addItemToItemsList}
/>
</div>
);
}
}
class ItemList extends React.Component {
render () {
const {items} = this.props;
return (
<div>
{items.map((item, index) => {
return (
<div key={index}>item.item_name</div>
)
})}
</div>
);
}
}
class AddItemForm extends React.Component {
constructor(props) {
super(props);
this.state = {
item: {
item_name : '',
comment:{}
}
};
}
handleChange = (event) => {
const new_item = Object.assign({}, this.state.item, {item_name: event.target.value});
this.setState({
item: new_item
});
}
handleSubmit = (event) => {
event.preventDefault();
this.props.addItemToItemsList(this.state.item);
}
render() {
return (
<form onSubmit={this.handleSubmit}>
<label>
<input type="text" item_name={this.state.item.item_name} onChange={this.handleChange} />
</label>
<input type="submit" value="Submit" />
</form>
);
}
}
export default AddItemForm;
I think, you have an error inside AddItemForm, you should pass onSubmit function from App to AddItemForm and change items through this function:
class App extends React.Component {
constructor(props) {
super(props);
this.state = {
items: []
}
this.handleSubmit = this.handleSubmit.bind(this);
};
handleSubmit(value){
this.setState({
items: this.state.items.concat(value)
})
}
render() {
return (
<div className="App">
<ItemList items={this.state.items} />
<AddItemForm
onSubmit={this.handleSubmit}
items={this.state.items} />
</div>
);
}
}
About main question, one of the way to solve this problem
const ItemList = ({items}) => (
<div>
{items.map( (item, index)=> (
<div key={index}>{item.item_name}</div>
))}
</div>
);
full working example here: https://codesandbox.io/s/7k624nz94q
You can't add to the array directly. You need to pass a callback that will add to the array in your parent component's state. This is a very common pattern when using react.
Here is a skeleton of what you need to do:
In your parent component, you don't need to pass the whole list to your AddItemForm component, just a addItem callback to your child component:
class App extends Component {
constructor(props){
super(props);
this.state = {
items: []
}
this.addItemToList = this.addItemToList.bind(this);
};
render() {
return (
<div className="App">
<ItemList items={this.state.items}/>
<AddItemForm addItemToList={this.addItemToList}/>
</div>
);
}
addItemToList(newValue) {
// Here you add the item to your state
// Always treat your state as immutable, so create a copy then add the item, then set your new State
const newArray = this.state.items.slice(); // clone
newArray .push(newValue); // Add value
this.setState({items: newArray}); // Set the new state
}
}
More info on how to add items to an array in the state here: React.js - What is the best way to add a value to an array in state
Then you use that callback in your child component:
handleSubmit(event) {
event.preventDefault();
// this.props.items.push(this.state.item);
// Here don't mutate the props, instead call the callback to add the item to your parent's component's state
this.props.addItemToList(this.state.item);
}
To display a list of items, you need to use the map function: https://reactjs.org/docs/lists-and-keys.html#rendering-multiple-components