Develop Reference

ReactJS onClick not working on first element in menu

I'm making a custom dropdown list in reactjs. When I click on any element in the dropdown list I get it's value and put it inside an input and it works just fine. The problem is that the first element returns nothing and I can't get it's value. Also I developed the dropdown list to disappear when I choose any element inside of it. But like I said it works just fine on all elements except the first one.
I solved the problem by setTimeOut and hide the dropdown list in 50 milliseconds. But I don't think this's a right solution.
//Select Component
class Select extends Component {
showList = (e) => {
e.target.closest('.select').classList.add('active');
}
hideList = (e) => {
setTimeout(() => {
e.target.closest('.select').classList.remove('active');
}, 100);
}
selectValue = (e) => {
let value = e.target.getElementsByTagName('span')[0].innerHTML;
this.setState({ selectValue: value })
}
render() {
return (
<input
{...this.props}
type="text"
placeholder={this.props['placeholder']}
onFocus={this.showList}
onBlur={this.hideList}
value={this.state.selectValue}
onChange={this.changeSelectValue}
required
/>
<div className="select">
<div className="select-options menu full-width">
{
this.props.list.map(element => {
return (
<MenuItem text={element} onClick={(e) => this.selectValue(e)} />
)
})
}
</div>
</div>
);
}
}
==================
class MenuItem extends Component {
constructor(props) {
super(props);
this.state = {}
}
render() {
return (
<p className={"menu-item " + this.props['type'] } {...this.props}>
{this.props['icon'] ? <i className={this.props['icon']} ></i> : null}
<span>{this.props['text']}</span>
</p>
);
}
}

1.use key prop for every MenuItem Component when you are using the list to create a list of MenuItems.
2.Instead of getting value from target in selectValue function directly pass the value from onClick handler.
selectValue = (e , element) => {
this.setState({ selectValue: element })
}
<MenuItem text={element} key={element} onClick={(e) => this.selectValue(e , element)} />
Editted:-
Remove the onBlur handler and put the functionality of hideList inside selectValue function after setState,you can use setState with callback if normal setState doesn't work
selectValue = (e) => {
let value = e.target.getElementsByTagName('span')[0].innerHTML;
this.setState({ selectValue: value })
e.target.closest('.select').classList.remove('active');
}

How to use forEach in react js

I want to create a function which iterate over all element with same class and remove a specific class.
It could be done easily using JavaScript.
const boxes = document.querySelectorAll(".box1");
function remove_all_active_list() {
boxes.forEach((element) => element.classList.remove('active'));
}
But how can I do this similar thing is ReactJs. The problem which I am facing is that I can't use document.querySelectorAll(".box1") in React but, I can use React.createRef() but it is not giving me all elements, it's only giving me the last element.
This is my React Code
App.js
import React, { Component } from 'react';
import List from './List';
export class App extends Component {
componentDidMount() {
window.addEventListener('keydown', this.keypressed);
}
keypressed = (e) => {
if (e.keyCode == '38' || e.keyCode == '40') this.remove_all_active_list();
};
remove_all_active_list = () => {
// boxes.forEach((element) => element.classList.remove('active'));
};
divElement = (el) => {
console.log(el);
el.forEach((element) => element.classList.add('active'))
};
render() {
return (
<div className="container0">
<List divElement={this.divElement} />
</div>
);
}
}
export default App;
List.js
import React, { Component } from 'react';
import data from './content/data';
export class List extends Component {
divRef = React.createRef();
componentDidMount() {
this.props.divElement(this.divRef)
}
render() {
let listItem = data.map(({ title, src }, i) => {
return (
<div className="box1" id={i} ref={this.divRef} key={src}>
<img src={src} title={title} align="center" alt={title} />
<span>{title}</span>
</div>
);
});
return <div className="container1">{listItem}</div>;
}
}
export default List;
Please tell me how can I over come this problem.

The short answer
You wouldn't.
Instead you would conditionally add and remove the class to the element, the component, or to the collection.map() inside your React component.
Example
Here's an example that illustrates both:
import styles from './Example.module.css';
const Example = () => {
const myCondition = true;
const myCollection = [1, 2, 3];
return (
<div>
<div className={myCondition ? 'someGlobalClassName' : undefined}>Single element</div>
{myCollection.map((member) => (
<div key={member} className={myCondition ? styles.variant1 : styles.variant2}>
{member}
</div>
))}
</div>
);
};
export default Example;
So in your case:
You could pass active prop to the <ListItem /> component and use props.active as the condition.
Alternatively you could send activeIndex to <List /> component and use index === activeIndex as the condition in your map.
Explanation
Instead of adding or removing classes to a HTMLElement react takes care of rendering and updating the whole element and all its properties (including class - which in react you would write as className).
Without going into shadow dom and why react may be preferable, I'll just try to explain the shift in mindset:
Components do not only describe html elements, but may also contain logic and behaviour. Every time any property changes, at the very least the render method is called again, and the element is replaced by the new element (i.e. before without any class but now with a class).
Now it is much easier to change classes around. All you need to do is change a property or modify the result of a condition (if statement).
So instead of selecting some elements in the dom and applying some logic them, you would not select any element at all; the logic is written right inside the react component, close to the part that does the actual rendering.
Further reading
https://reactjs.org/docs/state-and-lifecycle.html
Please don't hessitate to add a comment if something should be rephrased or added.

pass the ref to the parent div in List component.
...
componentDidMount() {
this.props.divElement(this.divRef.current)
}
...
<div ref={this.divRef} className="container1">{listItem}</div>
then in App
divElement = (el) => {
console.log(el);
el.childNodes.forEach((element) => element.classList.add('active'))
}
hope this will work. here is a simple example
https://codesandbox.io/s/staging-microservice-0574t?file=/src/App.js

App.js
import React, { Component } from "react";
import List from "./List";
import "./styles.css";
export class App extends Component {
state = { element: [] };
ref = React.createRef();
componentDidMount() {
const {
current: { divRef = [] }
} = this.ref;
divRef.forEach((ele) => ele?.classList?.add("active"));
console.log(divRef);
window.addEventListener("keydown", this.keypressed);
}
keypressed = (e) => {
if (e.keyCode == "38" || e.keyCode == "40") this.remove_all_active_list();
};
remove_all_active_list = () => {
const {
current: { divRef = [] }
} = this.ref;
divRef.forEach((ele) => ele?.classList?.remove("active"));
// boxes.forEach((element) => element.classList.remove('active'));
console.log(divRef);
};
render() {
return (
<div className="container0">
<List divElement={this.divElement} ref={this.ref} />
</div>
);
}
}
export default App;
List.js
import React, { Component } from "react";
import data from "./data";
export class List extends Component {
// divRef = React.createRef();
divRef = [];
render() {
let listItem = data.map(({ title, src }, i) => {
return (
<div
className="box1"
key={i}
id={i}
ref={(element) => (this.divRef[i] = element)}
>
<img src={src} title={title} align="center" alt={title} width={100} />
<span>{title}</span>
</div>
);
});
return <div className="container1">{listItem}</div>;
}
}
export default List;
Create ref for List component and access their child elements. When key pressed(up/down arrow) the elements which has classname as 'active' will get removed. reference

Render unique divs for each hovered element

minimum reproducible example: https://codesandbox.io/s/react-hover-example-tu1eu?file=/index.js
I currently have a new element being rendered when either of 2 other elements are hovered over. But i would like to render different things based upon which element is hovered.
In the example below and in the codepen, there are 2 hoverable divs that are rendered; when they are hovered over, it changes the state and another div is rendered. I would like for the HoverMe2 div to render text "hello2". Currently, whether i hover hoverme1 or 2, they both just render the text "hello".
import React, { Component } from "react";
import { render } from "react-dom";
class HoverExample extends Component {
constructor(props) {
super(props);
this.handleMouseHover = this.handleMouseHover.bind(this);
this.state = {
isHovering: false
};
}
handleMouseHover() {
this.setState(this.toggleHoverState);
}
toggleHoverState(state) {
return {
isHovering: !state.isHovering
};
}
render() {
return (
<div>
<div
onMouseEnter={this.handleMouseHover}
onMouseLeave={this.handleMouseHover}
>
Hover Me
</div>
<div
onMouseEnter={this.handleMouseHover}
onMouseLeave={this.handleMouseHover}
>
Hover Me2
</div>
{this.state.isHovering && <div>hello</div>}
</div>
);
}
}
render(<HoverExample />, document.getElementById("root"));

You need to keep the state of item which you have hovered that's for sure
const { Component, useState, useEffect } = React;
class HoverExample extends Component {
constructor(props) {
super(props);
this.handleMouseHover = this.handleMouseHover.bind(this);
this.state = {
isHovering: false,
values: ['hello', 'hello2'],
value: 'hello'
};
}
handleMouseHover({target: {dataset: {id}}}) {
this.setState(state => {
return {
...state,
isHovering: !state.isHovering,
value: state.values[id]
};
});
}
render() {
return (
<div>
<div
data-id="0"
onMouseEnter={this.handleMouseHover}
onMouseLeave={this.handleMouseHover}
>
Hover Me
</div>
<div
data-id="1"
onMouseEnter={this.handleMouseHover}
onMouseLeave={this.handleMouseHover}
>
Hover Me2
</div>
{this.state.isHovering && <div>{this.state.value}</div>}
</div>
);
}
}
ReactDOM.render(
<HoverExample />,
document.getElementById('root')
);
<script src="https://unpkg.com/react/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone#6/babel.min.js"></script>
<div id="root"></div>

You can pass the context text as shown in example. This is working code:
import React, { Component } from "react";
import { render } from "react-dom";
// Drive this using some configuration. You can set based on your requirement.
export const HOVER_Hello1 = "Hello1";
export const HOVER_Hello2 = "Hello2";
class HoverExample extends Component {
constructor(props) {
super(props);
this.handleMouseHover = this.handleMouseHover.bind(this);
this.state = {
isHovering: false,
contextText: ""
};
}
handleMouseHover = (e, currentText) => {
this.setState({
isHovering: !this.state.isHovering,
contextText: currentText
});
}
toggleHoverState(state) {
//
}
render() {
return (
<div>
<div
onMouseEnter={e => this.handleMouseHover(e, HOVER_Hello1)}
onMouseLeave={e => this.handleMouseHover(e, HOVER_Hello1)}
>
Hover Me
</div>
<div
onMouseEnter={e => this.handleMouseHover(e, HOVER_Hello2)}
onMouseLeave={e => this.handleMouseHover(e, HOVER_Hello2)}
>
Hover Me2
</div>
{this.state.isHovering && <div>{this.state.contextText}</div>}
</div>
);
}
}
export default HoverExample;

If the whole point is about linking dynamically messages to JSX-element you're hovering, you may store that binding (e.g. within an object).
Upon rendering, you simply pass some anchor (e.g. id property of corresponding object) within a custom attribute (data-*), so that later on you may retrieve that, look up for the matching object, put linked message into state and render the message.
Following is a quick demo:
const { Component } = React,
{ render } = ReactDOM,
rootNode = document.getElementById('root')
const data = [
{id:0, text: 'Hover me', message: 'Thanks for hovering'},
{id:1, text: 'Hover me too', message: 'Great job'}
]
class HoverableDivs extends Component {
state = {
messageToShow: null
}
enterHandler = ({target:{dataset:{id:recordId}}}) => {
const {message} = this.props.data.find(({id}) => id == recordId)
this.setState({messageToShow: message})
}
leaveHandler = () => this.setState({messageToShow: null})
render(){
return (
<div>
{
this.props.data.map(({text,id}) => (
<div
key={id}
data-id={id}
onMouseEnter={this.enterHandler}
onMouseLeave={this.leaveHandler}
>
{text}
</div>
))
}
{
this.state.messageToShow && <div>{this.state.messageToShow}</div>
}
</div>
)
}
}
render (
<HoverableDivs {...{data}} />,
rootNode
)
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.12.0/umd/react.production.min.js"></script><script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.11.0/umd/react-dom.production.min.js"></script><div id="root"></div>

As #CevaComic pointed out, you can do this with CSS. But if you want to use React, for example, because your actual problem is more complex, here is the answer.
You will need a way to tell apart the two elements. It could be done with some neat tricks, like setting an unique id to each element, passing a custom argument, or something else.
But I would advise against "cool tricks" as it's more difficult to understand what is going on, and the code is more prone to errors. I think the best way it to use a dumb approach of unique functions for unique elements.
Each onMouseEnter and onMouseLeave has to be an unique function (e.g. handleMouseHover1 and handleMouseHover2), and each of those functions need to control unique state (for example, isHovering1 and isHovering2). Then you have to render the element you want based on the state. Of course, for a real-world code, you will probably want to use more descriptive names to make the code more comprehensible. The full code would look something like this.
class HoverExample extends Component {
state = {
isHovering1: false,
isHovering2: false
};
handleMouseHover1 = () => {
this.setState(({ isHovering1 }) => ({ isHovering1: !isHovering1 }));
};
handleMouseHover2 = () => {
this.setState(({ isHovering2 }) => ({ isHovering2: !isHovering2 }));
};
render() {
const { isHovering1, isHovering2 } = this.state;
return (
<div>
<div
onMouseEnter={this.handleMouseHover1}
onMouseLeave={this.handleMouseHover1}
>
Hover Me1
</div>
<div
onMouseEnter={this.handleMouseHover2}
onMouseLeave={this.handleMouseHover2}
>
Hover Me2
</div>
{isHovering1 && <div>hello1</div>}
{isHovering2 && <div>hello2</div>}
</div>
);
}
}
Also, updated example: https://codesandbox.io/s/react-hover-example-rc3h0
Note: I have also edited the code to add some syntax sugar which exists with newer ECMAScript versions. Instead of binding the function, you can use the arrow function format, e.g. fn = () => { ... }. The arrow function means the this context is automatically bound to the function, so you don't have to do it manually. Also, you don't have to initialize this.state inside the constructor, you can define it as a class instance property. With those two things together, you do not need the constructor at all, and it makes the code a bit cleaner.

Handling state with multiple checkboxes in React Native

I have a simple form with two checkboxes for someone to choose one or the other i.e Yes or No not both. Am using the React-native-element toolkit as shown below.
export default class CheckerForm extends React.Component {
state = {
checked: false,
}
handleYesCheck =() => {
this.setState({checked: !this.state.checked})
}
handleNoCheck =() => {
this.setState({checked: !this.state.checked})
}
render(){
const { checked } = this.state
return (
<View>
<CheckBox
center
title='Yes'
checked={checked}
onPress={this.handleYesCheck}
/>
<CheckBox
center
title='No'
checked={checked}
onPress={this.handleNoCheck}
/>
<View>
I want to capture and modify the state of the checkboxes but when I click one of the checkboxes I modify the state of the other i.e both will be checked and unchecked. How can I modify the states of the checkboxes independently such that when I click on Yes, No is unchecked and vice versa? Generally what is the best way to capture the state so that I can use it.

What you can do is have a array of checkboxes, and save in the state the index of the checked one.
state = {
checkedId: -1,
checkboxes: [{
id: "yes",
title: "Yes"
}, {
id: "no",
title: "No"
}]
}
handleCheck = (checkedId) => {
this.setState({
checkedId
})
}
render() {
const {
checkboxes,
checkedId
} = this.state
return ( <
View > {
checkboxes.map(checkbox => ( <
CheckBox center key = {
checkbox.id
}
title = {
checkbox.title
}
checked = {
checkbox.id == checkedId
}
onPress = {
() => this.handleCheck(checkbox.id)
}
/>
)
} <
View >
)
}
This way you can also handle more than two checkboxes and also know which one is checked by the index.

when I click add button multiple times it should show I am here div with delete button with multiple times

I am trying to build a simple ui so that I can learn react.
right now when I click an add button it will show I am here div and delete button
when I click add button multiple times it should show I am here div with delete button with multiple times.
so I research and found this example https://www.skptricks.com/2018/06/append-or-prepend-html-using-reactjs.html
using this example I implemented the appendData method but still its not adding the div multiple times.
in my console I am able to see how many times divs are added console.log("this.displayData---->", this.displayData);
can you tell me how to fix it.
so that in future I will fix it myself
https://stackblitz.com/edit/react-b2d3rb?file=demo.js
onClick = () => {
this.setState({ showResults: true });
this.setState({ showOrHideSearch: true });
this.displayData.push(
<div style={{ display: this.state.showOrHideSearch ? "" : "none" }}>
{" "}
I am here
<input
ref="rbc-toolbar-label"
type="submit"
value="Delete"
onClick={this.onDelete}
/>
</div>
);
console.log("this.displayData---->", this.displayData);
this.setState({ showdata: this.displayData });
};

First thing is you should not use this.setState multiple times, instead you should do them in one line. And instead of pushing data into class variables, you should set that data into your state variable and the same variable you should use in your render function. It will be good if you can share your complete code..

import React, { Component } from 'react';
import Calendar from 'rc-calendar';
import DatePicker from 'rc-calendar/lib/Picker';
import 'rc-calendar/assets/index.css';
import moment from 'moment';
class CalendarPage extends Component {
constructor(props) {
super(props);
console.log("AsyncValidationForm this.props---->", this.props);
this.state = {
displayData: []
};
}
onClick = () => {
let displayData = [...this.state.displayData];
displayData.push( { text: 'I am here' });
this.setState({ displayData: displayData });
};
onDelete = index => {
let displayData = [...this.state.displayData];
if(index > -1){
displayData.splice(index, 1);
}
this.setState({ displayData: displayData });
};
handleChange = name => event => {
const value = event.target.value;
this.setState(
{
[name]: value,
pristine: false
},
() => {
this.props.handleChange(name, value); //setState username, password of VerticalLinearStepper.js
}
);
};
onSubmit(event) {
event.preventDefault();
var newItemValue = this.refs.itemName.value;
if(newItemValue) {
this.props.addItem({newItemValue});
this.refs.form.reset();
}
}
render() {
const { handleSubmit, pristine, reset, submitting } = this.props;
let { displayData} = this.state;
return (
<form onSubmit={handleSubmit}>
<div>
<input type="submit" value="add" onClick={this.onClick} />
{displayData.length > 0 ? displayData.map(function(data, index) {
return (
<div key={index}>
{data.text} - For testing added index on screen {index}
<input
ref="rbc-toolbar-label"
type="submit"
value="Delete"
onClick={() => this.onDelete(index)}
/>
</div>
)}, this) : null}
</div>
</form>
);
}
}
export default CalendarPage;