Develop 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.

Updating child Components with state change in Reactjs

So I know this question has been asked a couple of times and the general concession is that props cant be changed when it has already passed down to a child. The situation I have here is that basically i have a different onClick function in a different file that updates the the id="movie-header" with an innerHTML, the DOMSubtreeModified and componentDidUpdatedetects the change and pass down the new props to Child "Ebay".
So the question here is how do I get the Ebay component to update its state and make use of the new value with every change to the state in the moviemodalwindow(the parent of the Ebay)
MovieModalWindow.js
import React from "react";
import "../MovieGo.css";
import Ebay from "../Store/Ebay";
class MovieModalWindow extends React.Component {
constructor() {
super();
this.state = {
name: 1
};
}
componentDidMount() {
var element = document.getElementById("movie-header");
element.addEventListener("DOMSubtreeModified", this.myFunction(element));
var name = this.state.name + 1;
this.setState({ name: [...this.state.name, name] });
}
myFunction = input => event => {
this.setState({ name: input.innerHTML });
};
componentDidUpdate(prevProps, prevState) {
if (prevState.name != this.state.name) {
window.localStorage.setItem("keyword", this.state.name);
}
}
render() {
return (
<div id="myModal" class="modal">
<div class="modal-content">
<span onClick={onClose} class="close">
×
</span>
<h1 id="movie-header" />
<div className="middle-window">
<div className="left">
<Ebay id="ebay" keyword={this.state.name} />
</div>
</div>
<h3>PLOT</h3>
<p id="moviedetails" />
</div>
</div>
);
}
}
export default MovieModalWindow;
Ebay.js File
import React from "react"
class Ebay extends React.Component{
constructor(){
super();
this.state={
data:[],
}
}
componentWillUpdate(prevProps, prevState){
if (prevProps.keywords!=this.props.keywords){
console.log(window.localStorage.getItem("keyword"))
}
render(){
const{newInput} =this.props
return(
<div>
</div>
)
}
}
export default Ebay

I'm unsure if I'm answering the question you're asking, so apologies if this isn't what you're asking.
Step 1. Make Ebay's prop's change when you need this update to happen. (I think you stated you already have this occurring?)
Step 2: Make Ebay's state update when the props change. Here you can just watch for prop changes with componentWillReceiveProps and update the state accordingly.
class Ebay extends React.Component {
constructor() {
super();
this.state = { data: [] };
}
componentWillRecieveProps(nextProps) {
if (nextProps.keyword !== this.props.keyword) {
this.setState({ data: ['something new'] });
}
}
render() { ... }
}

Render a component from another class using function

So, I have a class like this:
class Blah extends Component {
constructor(props) {
super(props);
}
handleComponent = (event) => {
let divid = event.target.getAttribute('id');
if (divid === 'col') {
// I want to render component by this condition
} else if (divid === 'ro') {
// or I want to render component by this condition
} else {
//or I want to render component by this condition
}
};
render() {
const { classes } = this.props;
return (
<div>
<div id = 'col' onClick={this.handleComponent}>Sheep</div>
<div id = 'ro' onClick={this.handleComponent}>Cow</div>
<div id = 'ball' onClick={this.handleComponent}>Dog</div>
{ I want to render my component here after click }
</div>
);
}
}
I have another class written on top of this:
class Flow extends Component {
constructor(props){
super(props);
};
render() {
return(
<div style={{background:'somecolor'...blah blah}}>Clap</div>
);
}
}
And I am Passing this by:
var foo = withStyles(styles)(Flow)
I have tried returning components but I am not getting anywhere.
I can use ternary operator but it still will render only one of two but I have three component have three design for each of them.
I want to render one of them to render on some condition as stated above.
If I use states that for toggle that will too have two components for render. Don't go on the code, this is made up, So any Ideas ? Fragments ? Any help will be appreciated. Thank you.

To render component by condition simply use switch statement.
In my example we use state to store current active component.
renderMyComponent method takes care of rendering one of three possible components.
handleChange method changes current state and triggers new render of App component.
This example use class properties plugin.
renderMyComponent = () => {
means autobind and is the same as using in constuctor method
this.renderMyComponent = this.renderMyComponent.bind(this);
Working example:
const ComponentOne = () => <div>Hi, i am component one</div>;
const ComponentTwo = () => <div>Hi, i am component two</div>;
const ComponentThree = () => <div>Hi, i am component three</div>;
class App extends React.Component {
state = { current: 0 }
renderMyComponent = () => {
// Our switch conditional render
switch(this.state.current) {
case 0:
return <ComponentOne />;
case 1:
return <ComponentTwo />;
case 2:
return <ComponentThree />;
default:
return null;
}
}
handleChange = (event) => {
// We are looking for data-trigger attribute
// In this example we expect type number but trigger holds string
// That's why we 'cast' to a number using Number()
const current = Number(event.target.dataset.trigger);
// Sets new state of current component and triggers new render
this.setState({ current })
}
render() {
return (
<div>
<div>
Pick component to render
<button
type="button"
data-trigger="0"
onClick={this.handleChange}
>
Render 1
</button>
<button
type="button"
data-trigger="1"
onClick={this.handleChange}
>
Render 2
</button>
<button
type="button"
data-trigger="2"
onClick={this.handleChange}
>
Render 3
</button>
</div>
{this.renderMyComponent()}
</div>
)
}
}
ReactDOM.render(<App />, 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>
Reviewing your code:
You don't need constructor here.
...
constructor(props){
super(props);
}
...

Render Random Item from State React.JS

Given some items stored in state, I want to be able to click a button and display a random item from that array. So far it only works on the first click and then it displays the same one letter after the first click.
What exactly is going on?
import React, { Component } from 'react'
export default class App extends Component {
constructor(props) {
super(props)
this.state = {
notes: ['hey', 'yo', 'sup'],
clicked: false
}
}
handleClick = () => {
this.setState({
clicked: true,
notes: this.state.notes[Math.floor(Math.random() *
this.state.notes.length)]
})
}
render() {
return (
<div className="App">
<button onClick={this.handleClick}>Random Note</button>
<h1>{this.state.clicked ? this.state.notes : ''}</h1>
</div>
)
}
}

Add selected note handling
import React, { Component } from 'react'
export default class App extends Component {
constructor(props) {
super(props)
this.state = {
notes: ['hey', 'yo', 'sup'],
selectedNote: null,
clicked: false
}
}
handleClick = () => {
this.setState({
clicked: true,
selectedNote: this.state.notes[Math.floor(Math.random() *
this.state.notes.length)]
})
}
render() {
return (
<div className="App">
<button onClick={this.handleClick}>Random Note</button>
<h1>{this.state.clicked && this.state.selectedNote}</h1>
</div>
)
}
}

You're overwriting the notes array in state in your handleClick method. Try using a different key (something like activeNote) in handleClick, then use that in your render method rather than this.state.notes.

So I think I solved it.
I ended up adding another state key randomWord and setting it equal to ''.
I then set the state of randomWord to that of this.state.notes when randomized.
Finally, I rendered this.state.randomWord
No clue if that's the correct approach but it's a working solution, lol.

Access a React component method / state from outside the component

I have embedded a reactjs component into an existing HTML page by referencing it's ID like described in React's tutorial:
ReactDOM.render(
<Page />,
document.getElementById('my-react-compnent')
);
Then:
<div id="my-react-compnent></div>
The component is displayed and works as expected.
Now I want to link a button located on that page to my component (to be specific I would like to retrive its state, but for the example even invoking one of its methods would be fine).
In other words - when clicking the outside button, I want to invoke a method from the Page component?
How can I do that?

The Old Recommendation
Assigning the returned value from ReactDOM.render does allow access to the component and it's methods. For example, in a simple app, we might have:
const PageComponent = ReactDOM.render(<Page />, document.getElementById("app"));
which we can then access using PageComponent, and any of its methods can be accessed with PageComponent.METHOD.
However, according to the docs this might be changed or deprecated and is not recommended.
The New Recommendation
The new recommendation is to attach a callback ref to the root element. Using the same example above:
const PageComponent = ReactDOM.render(<Page ref={(pageComponent) => {window.pageComponent = pageComponent}}/>, document.getElementById("app"));
which we can then access using window.pageComponent, and any of its methods can be accessed with window.pageComponent.METHOD.
This also works for child components.
Here's a full example:
class ChildComponent extends React.Component {
constructor(props) {
super(props);
this.state = {
counter: 0
}
}
returnCounter = () => {
return this.state.counter;
}
increment = (event) => {
event.stopPropagation();
this.setState(prevState => {
return {
counter: prevState.counter + 1
}
})
}
render() {
return (
<div onClick={this.increment}>
Child Value - {this.state.counter} - Click to increment
</div>
)
}
}
class Page extends React.Component {
constructor(props) {
super(props);
this.state = {
counter: 0
}
}
returnCounter = () => {
return this.state.counter;
}
increment = () => {
this.setState(prevState => {
return {
counter: prevState.counter + 1
}
})
}
render() {
return (
<div onClick={this.increment}>
<div>Parent Value - {this.state.counter} - Click to increment</div>
<ChildComponent ref={(childComponent) => {window.childComponent = childComponent}}/>
</div>
)
}
}
ReactDOM.render(<Page ref={(pageComponent) => {window.pageComponent = pageComponent}} />, document.getElementById("app"));
const parentBtn = document.getElementById("parentButton");
parentBtn.addEventListener("click", event => {
alert(window.pageComponent.returnCounter());
});
const childBtn = document.getElementById("childButton");
childBtn.addEventListener("click", event => {
alert(window.childComponent.returnCounter());
});
<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="app"></div>
<button id="parentButton">Get Parent State</button>
<button id="childButton">Get Child State</button>