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How do you update state in functional components in React?

I'm running into the issue where I have created a functional component to render a dropdown menu, however I cannot update the initial state in the main App.JS. I'm not really sure how to update the state unless it is in the same component.
Here is a snippet of my App.js where I initialize the items array and call the functional component.
const items = [
{
id: 1,
value:'item1'
},
{
id: 2,
value:'item2'
},
{
id: 3,
value:'item3'
}
]
class App extends Component{
state = {
item: ''
}
...
render(){
return{
<ItemList title = "Select Item items= {items} />
And here is my functional componenet. Essentially a dropdown menu from a YouTube tutorial I watched (https://www.youtube.com/watch?v=t8JK5bVoVBw).
function ItemList ({title, items, multiSelect}) {
const [open, setOpen] = useState (false);
const [selection, setSelection] = useState([]);
const toggle =() =>setOpen(!open);
ItemList.handleClickOutside = ()=> setOpen(false);
function handleOnClick(item) {
if (!selection.some(current => current.id == item.id)){
if (!multiSelect){
setSelection([item])
}
else if (multiSelect) {
setSelection([...selection, item])
}
}
else{
let selectionAfterRemoval = selection;
selectionAfterRemoval = selectionAfterRemoval.filter(
current =>current.id == item.id
)
setSelection([...selectionAfterRemoval])
}
}
function itemSelected(item){
if (selection.find(current =>current.id == item.id)){
return true;
}
return false;
}
return (
<div className="dd-wraper">
<div tabIndex={0}
className="dd-header"
role="button"
onKeyPress={() => toggle(!open)}
onClick={() =>toggle(!open)}
onChange={(e) => this.setState({robot: e.target.value})}
>
<div className="dd-header_title">
<p className = "dd-header_title--bold">{title}</p>
</div>
<div className="dd-header_action">
<p>{open ? 'Close' : 'Open'}</p>
</div>
</div>
{open && (
<ul className ="dd-list">
{item.map(item =>(
<li className="dd-list-item" key={item.id}>
<button type ="button"
onClick={() => handleOnClick(item)}>
<span>{item.value}</span>
<span>{itemSelected(item) && 'Selected'}</span>
</button>
</li>
))}
</ul>
)}
</div>
)
}
const clickOutsideConfig ={
handleClickOutside: () => RobotList.handleClickOutside
}
I tried passing props and mutating the state in the functional component, but nothing gets changed. I suspect that it needs to be changed in the itemSelected function, but I'm not sure how. Any help would be greatly appreciated!

In a function component, you have the setters of the state variables. In your example, you can directly use setOpen(...) or setSelection(...). In case of a boolean state variable, you could just toggle by using setOpen(!open). See https://reactjs.org/docs/hooks-state.html (Chapter "Updating State") for further details.

So you need to do something like below . Here we are passing handleChange in parent Component as props to the child component and in Child Component we are calling the method as props.onChange
Parent Component:
class Parent extends React.Component {
constructor(props) {
super(props)
this.state = {
value :''
}
}
handleChange = (newValue) => {
this.setState({ value: newValue });
}
render() {
return <Child value={this.state.value} onChange = {this.handleChange} />
}
}
Child Component:
function Child(props) {
function handleChange(event) {
// Here, we invoke the callback with the new value
props.onChange(event.target.value);
}
return <input value={props.value} onChange={handleChange} />
}

How to invoke button click in List in Reactjs

I want to have 3 buttons and 3 related components . So that when button click show its related component . Here is my code :
Main Component :
class Main extends Component { constructor(props) {
super(props);
this.state = {
show: false,
}}
onClick(e) {
e.preventDefault()
console.log(e.target.id)
this.setState({ show: !this.state.show }); }
renderTabs() {
var child = this.props.child;
var items = [];
__.forEach(child, (item, index) => {
items.push(
<div>
<Button id={index} onClick={(e) => this.onClick(e)}>{item.data}</Button>
{this.state.show ? (
<CropComponent title={item.data} opts={item.opts} data={item.child} />
) : null}
</div>
);
});
return items;
}
render() {
var opts = this.props.opts;
return (
<div>
{this.renderTabs()}
</div>
)}
}
export default Main;
And here is my CropComponent :
class CropComponent extends Component {
constructor(props) {
super(props);
this.state = {
};
}
render() {
return (
<div>hello {this.props.data}</div>
);
}
}
export default CropComponent;
Here are my buttons how can i show its related component when click on a button and hide it on re-click the same button ?

Maintain a show state with initial value as -1. Supply event and index to onClick. In onClick do setState of show as index.
Check if show === index and render the corresponding component.
Like this
this.state = {
show: -1
}
onClick(e,index) {
e.preventDefault()
this.setState({ show: show===index? -1 : index});
}
__.forEach(child, (item, index) => {
items.push(
<div>
<Button id={index} onClick={(e) => this.onClick(e,index)}>{item.data}</Button>
{this.state.show === index ? (
<CropComponent title={item.data} opts={item.opts} data={item.child} />
) : null}
</div>
);
});
Edit:
updated the answer based on helpful comment by #Tony Nguyen

Stop Relay: Query Renderer in reloading data for certain setStates

I'm currently following this and I did get it to work. But I would like to know if there is a way to stop the Query Render from reloading the data when calling this.setState(). Basically what I want is when I type into the textbox, I don't want to reload the data just yet but due to rendering issues, I need to set the state. I want the data to be reloaded ONLY when a button is clicked but the data will be based on the textbox value.
What I tried is separating the textbox value state from the actual variable passed to graphql, but it seems that regardless of variable change the Query will reload.
Here is the code FYR.
const query = graphql`
query TestComponentQuery($accountId: Int) {
viewer {
userWithAccount(accountId: $accountId) {
name
}
}
}
`;
class TestComponent extends React.Component{
constructor(props){
super(props);
this.state = {
accountId:14,
textboxValue: 14
}
}
onChange (event){
this.setState({textboxValue:event.target.value})
}
render () {
return (
<div>
<input type="text" onChange={this.onChange.bind(this)}/>
<QueryRenderer
environment={environment}
query={query}
variables={{
accountId: this.state.accountId,
}}
render={({ error, props }) => {
if (error) {
return (
<center>Error</center>
);
} else if (props) {
const { userWithAccount } = props.viewer;
console.log(userWithAccount)
return (
<ul>
{
userWithAccount.map(({name}) => (<li>{name}</li>))
}
</ul>
);
}
return (
<div>Loading</div>
);
}}
/>
</div>
);
}
}

Okay so my last answer didn't work as intended, so I thought I would create an entirely new example to demonstrate what I am talking about. Simply, the goal here is to have a child component within a parent component that only re-renders when it receives NEW props. Note, I have made use of the component lifecycle method shouldComponentUpdate() to prevent the Child component from re-rendering unless there is a change to the prop. Hope this helps with your problem.
class Child extends React.Component {
shouldComponentUpdate(nextProps) {
if (nextProps.id === this.props.id) {
return false
} else {
return true
}
}
componentDidUpdate() {
console.log("Child component updated")
}
render() {
return (
<div>
{`Current child ID prop: ${this.props.id}`}
</div>
)
}
}
class Parent extends React.Component {
constructor(props) {
super(props)
this.state = {
id: 14,
text: 15
}
}
onChange = (event) => {
this.setState({ text: event.target.value })
}
onClick = () => {
this.setState({ id: this.state.text })
}
render() {
return (
<div>
<input type='text' onChange={this.onChange} />
<button onClick={this.onClick}>Change ID</button>
<Child id={this.state.id} />
</div>
)
}
}
function App() {
return (
<div className="App">
<Parent />
</div>
);
}

Showing 1 of 2 components on button click

On the parent component, I am trying to do 2 buttons, each of them will show a component, the first button shows itemlist and second component shows itemlist2 but I couldn't seem to get it right, I tried to follow this example (https://codepen.io/PiotrBerebecki/pen/yaVaLK) even though I'm not sure its the right resource for such feature, here is my app.js code
class App extends Component {
state = {
one: false
};
handleClick(e) {
const userChoice = e.target.className;
this.setState({
userChoice
});
}
toggleDiv() {
this.setState({
one: !this.state.one
});
}
toggleDiv1() {
this.setState({
one: this.state.one
});
}
render() {
return (
<div>
<NavBar />
<div className="container-fluid">
<ServiceSelector toggleDiv={this.toggleDiv.bind(this)} toggleDiv1=
{this.toggleDiv1.bind(this)} />
{this.state.one == false ? <ItemList /> : <ItemList2 />}
</div>
</div>
);
}
}
class ServiceSelector extends React.Component {
toggleDiv() {
this.props.toggleDiv();
}
toggleDiv2() {
this.props.toggleDiv2();
}
render() {
return (
<div>
{" "}
<button onClick={this.toggleDiv.bind(this)}>sss </button>
<button onClick={this.toggleDiv1.bind(this)}>sss </button>
</div>
);
}
}

Actually, this function
toggleDiv1() {
this.setState({
one: this.state.one
});
}
is useless.
The toggle function should have one
toggleFunc() {
this.setState({stateWatched = !this.state.stateWatched})
}
Use this function in both case(set true or false). And don't bind when call in ServiceSelector component, this is nonesense.
class App extends Component {
state = {
one: false
};
handleClick(e) {
const userChoice = e.target.className;
this.setState({
userChoice
});
}
toggleDiv() {
this.setState({
one: !this.state.one
});
}
render() {
return (
<div>
<NavBar />
<div className="container-fluid">
<ServiceSelector toggleDiv={this.toggleDiv.bind(this)} />
{this.state.one == false ? <ItemList /> : <ItemList2 />}
</div>
</div>
);
}
}
class ServiceSelector extends React.Component {
render() {
return (
<div>
{" "}
<button onClick={this.props.toggleDiv}>sss </button>
</div>
);
}
}
If you want to have 2 buttons to handle toggle. Change the logic of the function.
function toggleTrue() {
this.setState({one: true})
}
function toggleFalse() {
this.setState({one: false})
}
and then pass it like normal (remember to remove bind function in a child component )

I am not too sure about what you trying to do but i am gonna give it a try.
class App extends Component {
state = {
one: false
};
handleClick(e) {
const userChoice = e.target.className;
this.setState({
userChoice
});
}
toggleDiv = () => {
this.setState({
one: !this.state.one
});
}
toggleDiv1 = () => {
this.setState({
one: this.state.one
});
}
render() {
return (
<div>
<NavBar />
<div className="container-fluid">
<ServiceSelector toggleDiv={this.toggleDiv} toggleDiv1={this.toggleDiv1} />
{this.state.one == false ? <ItemList /> : <ItemList2 />}
</div>
</div>
);
}
}
class ServiceSelector extends React.Component {
render() {
return (
<div>
{" "}
<button onClick={this.props.toggleDiv}>sss </button>
<button onClick={this.props.toggleDiv1}>sss </button>
</div>
);
}
}
Using arrow functions remove the need of typing this.bind as it does the binding for you
Let me know if it helps

React js: Accessing state of other components

I have a component built using the below code. The aim is to add a class on the card to highlight it when the button inside it is clicked. However, the below code works on the first click but doesn't work for the subsequent clicks.
I understood that I have to set the clicked state of other elements to false when I remove the class. How can this be done?
import React, { Component } from 'react';
import './PricingCard.css';
class PricingCard extends Component {
constructor(){
super();
this.state = {
clicked : false
}
}
makeSelection(){
let elems = document.getElementsByClassName('Card');
for(var i=0;i<elems.length;i++){
elems[i].classList.remove("active");
}
this.setState({clicked: true});
}
render() {
var activeClass = this.state.clicked ? 'active' : '';
return (
<div className= {"categoryItem Card " + this.props.planName + " " +activeClass}>
<div className="cardDetails">
<div> {this.props.planName} </div>
<div className="pricing"> {this.props.price} </div>
<button onClick={this.makeSelection.bind(this)} className="buttonPrimary"> Select this plan </button>
<div className="subtitle"> {this.props.footerText} </div>
</div>
</div>
);
}
}
export default PricingCard;

Wouldn't it be easier to have the logic in a parent component? Since it is "aware" of all the child Card components.
Have something like...
this.state = { selectedComponent: null };
onClick(card_id) {
this.setState({ selectedComponent: card_id });
}
...in render:
const cards = smth.map((card) =>
<Card onClick={this.onClick.bind(this, card.id)}
isActive={map.id === this.state.selectedComponent} />
Would this work?

Best way will be to lift lift the state up. Like this:
class PricingCardContainer extends React.Component {
constructor(props){
super(props);
this.state = {
selectedCard: NaN,
}
}
handleCardClick(selectedCard){ this.setState({ selectedCard }); }
render() {
return (
<div>{
this.props.dataArray.map((data, i) =>
<PricingCard
key={i}
className={this.state.selectedCard === i ? 'active': ''}
price={data.price}
onClick={() => this.handleCardClick(i)}
footerText={data.footerText}
planName={data.planName}
plan={data.plan}
/>
)
}</div>
)
}
}
const PricingCard = ({ className = '', planName, price, onClick, footerText }) => (
<div className= {`categoryItem Card ${planName} ${className}`}>
<div className="cardDetails">
<div> {planName} </div>
<div className="pricing"> {price} </div>
<button onClick={onClick} className="buttonPrimary"> Select this plan </button>
<div className="subtitle"> {footerText} </div>
</div>
</div>
);
export default PricingCard;
Although it would be better to use some data id than index value.