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How to call a function with arguments onclick of a button in a react component

Here is my function with arguments that i added in index.html in publics folder in a script tag
function displayContent(event, contentNameID) {
let content = document.getElementsByClassName("contentClass");
let totalCount = content.length;
for (let count = 0; count < totalCount; count++) {
content[count].style.display = "none";
}
let links = document.getElementsByClassName("linkClass");
totalLinks = links.length;
for (let count = 0; count < totalLinks; count++) {
links[count].classList.remove("active");
}
document.getElementById(contentNameID).style.display = "block";
event.currentTarget.classList.add("active");
}
Trying to call this function from click of buttons on my react component that looks like below
<button class="linkClass" onclick="displayContent(event, 'project2')">Meet at Campus
</button>
Please guide me with the syntax

Here's the correct syntax
<button className="linkClass" onClick={(event)=>displayContent(event,'project2')}>Meet at Campus</button>
Edit: please note that React components return JSX

It looks like you're trying to make some sort accordion but you shouldn't really be mixing vanilla JS with React as React needs control of the DOM.
So here's a brief example of how you might approach this using 1) state, and 2) a Panel component which comprises a button, and some content.
const { useState } = React;
function Example() {
// Initialise state with an array of false values
const [ state, setState ] = useState([
false, false, false
]);
// When a button in a panel is clicked get
// its id from the dataset, create a new array using `map`
// and then set the new state (at which point the component
// will render again
function handleClick(e) {
const { id } = e.target.dataset;
const updated = state.map((el, i) => {
if (i === id - 1) return true;
return false;
});
setState(updated);
}
// Pass in some props to each Panel component
return (
<div>
<Panel
name="Panel 1"
active={state[0]}
id="1"
handleClick={handleClick}
>
<span className="text1">Content 1</span>
</Panel>
<Panel
name="Panel 2"
active={state[1]}
id="2"
handleClick={handleClick}
>
<span className="text2">Content 2</span>
</Panel>
<Panel
name="Panel 3"
active={state[2]}
id="3"
handleClick={handleClick}
>
<span className="text3">Content 3</span>
</Panel>
</div>
);
}
function Panel(props) {
// Destructure those props
const {
name,
id,
active,
handleClick,
children
} = props;
// Return a div with a button, and
// content found in the children prop
// When the button is clicked the handler is
// called from the parent component, the state
// is updated, a new render is done. If the active prop
// is true show the content otherwise hide it
return (
<div className="panel">
<button data-id={id} onClick={handleClick}>
{name}
</button>
<div className={active && 'show'}>
{children}
</div>
</div>
);
}
ReactDOM.render(
<Example />,
document.getElementById('react')
);
.panel button:hover { cursor: pointer; }
.panel { margin: 1em 0; }
.panel div { display: none; }
.panel div.show { display: block; margin: 1em 0; }
.add { margin-top: 1em; background-color: #44aa77; }
.text1 { color: darkblue; font-weight: 600; }
.text2 { color: darkgreen; font-weight: 700; }
.text3 { color: darkred; font-weight: 300; }
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/17.0.2/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/17.0.2/umd/react-dom.production.min.js"></script>
<div id="react"></div>

Can't you use
document.getElementById("linkClass").onclick = () =>{
displayContent();
}
by giving the element an id with same of the class?

JS Image Slider with specific text to each image

I've followed a tutorial about JS image sliders. I'm trying to have a text box display on each image (figured that out) but I need the text to be specific for each image. The images being grabbed from an img folder and are in order (image-0, image-1, etc). I'm guessing I'll need some array but I can't figure out how to do this in JS and have the corresponding text display on each correct image. Code provided. Any help?
HTML
<body>
<div class="images">
<div id="btns">
<button type="button" class="btn prevBtn">↩</button>
<button type="button" class="btn nextBtn">↪</button>
</div>
<div id="textBlock">
<h4>This is the image</h4>
</div>
</div>
<script src="script.js"></script>
</body>
JS
const nextBtn = document.querySelector(".nextBtn");
const prevBtn = document.querySelector(".prevBtn");
const container = document.querySelector(".images");
let counter = 0;
nextBtn.addEventListener("click",nextSlide);
prevBtn.addEventListener("click",prevSlide);
function nextSlide () {
container.animate([{opacity:"0.1"},{opacity:"1.0"}],{duration:1000,fill:"forwards"});
if(counter === 4){
counter = -1;
}
counter++;
container.style.backgroundImage = `url(img/image-${counter}.jpg`
}
function prevSlide () {
container.animate([{opacity:"0.1"},{opacity:"1.0"}],{duration:1000,fill:"forwards"});
if(counter === 0){
counter = 5;
}
counter--;
container.style.backgroundImage = `url(img/image-${counter}.jpg`
}

Since you counter is indexed 0 and goes up to 𝑛 all you need is an array:
const descriptions = [
"A nice walk in the park", // for the image counter 0
"My dog and me", // for the image counter 1
// etc.
];
than all you need to do is:
textBlock.textContent = descriptions[counter];
But...
I don't know where you found that toturial but it's a really a great example on how not to build a gallery. The animation is odd, it's overly simplistic and cannot account for multiple galleries. It's repetitive and unmodular. And the total number of slides should never be hardcoded, that's why we use a programming language after all. And yes, it can count the number of items using .length.
Code should be reusable:
class Gallery {
constructor(id, slides) {
this.slides = slides || [];
this.total = this.slides.length;
this.curr = 0;
this.EL = document.querySelector(id);
this.EL_area = this.EL.querySelector(".Gallery-area");
this.EL_prev = this.EL.querySelector(".Gallery-prev");
this.EL_next = this.EL.querySelector(".Gallery-next");
this.EL_desc = this.EL.querySelector(".Gallery-desc");
const NewEL = (tag, prop) => Object.assign(document.createElement(tag), prop);
// Preload images
this.ELs_items = this.slides.reduce((DF, item) => (DF.push(NewEL("img", item)), DF), []);
this.EL_area.append(...this.ELs_items);
// Events
this.EL_prev.addEventListener("click", () => this.prev());
this.EL_next.addEventListener("click", () => this.next());
// Init
this.anim();
}
// Methods:
anim() {
this.curr = this.curr < 0 ? this.total - 1 : this.curr >= this.total ? 0 : this.curr;
this.ELs_items.forEach((EL, i) => EL.classList.toggle("is-active", i === this.curr));
this.EL_desc.textContent = this.slides[this.curr].alt;
}
prev() {
this.curr -= 1;
this.anim();
}
next() {
this.curr += 1;
this.anim();
}
}
// Use like:
new Gallery("#gallery-one", [
{alt: "My fluffy dog and me", src: "https://picsum.photos/400/300"},
{alt: "Here, we seem happy!", src: "https://picsum.photos/300/300"},
{alt: "We are making pizza?", src: "https://picsum.photos/600/300"},
]);
.Gallery {
position: relative;
height: 300px;
max-height: 100vh;
}
.Gallery-area > * {
position: absolute;
left: 0;
top: 0;
width: 100%;
height: 100%;
object-fit: cover;
transition: opacity 0.3s;
opacity: 0;
}
.Gallery-area > *.is-active {
opacity: 1;
}
.Gallery-btns {
position: absolute;
bottom: 20px;
width: 100%;
text-align: center;
}
.Gallery-desc {
position: absolute;
top: 20px;
width: 100%;
text-align: center;
font-size: 3em;
}
<div class="Gallery" id="gallery-one">
<div class="Gallery-area"></div>
<div class="Gallery-btns">
<button type="button" class="btn Gallery-prev">←</button>
<button type="button" class="btn Gallery-next">→</button>
</div>
<div class="Gallery-desc"></div>
</div>

Focused elements display wrong style

I have element with width 400% and I want to move it to left by using translateX(-(index/4)*100%) when focused index changes.
Changing focused element translateX property with tab keyboard button displays it wrong on middle elements (1,2) even though using same hardcoded styling works as expected. What am I missing here?
const {useState} = React;
const App = () => {
const [curr, setCurr] = useState(0);
const carouselStyles = {
transform: `translateX(${-(curr / 4) * 100}%)`
// uncomment to see that styling works fine with hardcoded values 1,2..
// transform: `translateX(${-(1 / 4) * 100}%)`
};
const handleFocus = (num) => {
if (num !== curr) {
setCurr(num);
}
};
console.log(carouselStyles);
return (
<div>
<div className="carousel" style={carouselStyles}>
<div className="item">
11 very long text
<a href="/111" onFocus={() => handleFocus(0)}>
11111
</a>
</div>
<div className="item">
22 very long text
<a href="/222" onFocus={() => handleFocus(1)}>
22222
</a>
</div>
<div className="item">
33 very long text
<a href="/333" onFocus={() => handleFocus(2)}>
33333
</a>
</div>
<div className="item">
44 very long text
<a href="/444" onFocus={() => handleFocus(3)}>
44444
</a>
</div>
</div>
current: {curr}
</div>
);
}
// Render it
ReactDOM.render(
<App />,
document.getElementById("react")
);
.carousel {
display: flex;
align-items: center;
width: 400%;
}
.item {
flex: 0 1 100%;
text-align: center;
border: 1px solid black;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.4/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.4/umd/react-dom.production.min.js"></script>
<div id="react"></div>

I needed to prevent the scrolling and in my provided example its enough to add this line into handleFocus function
window.scrollTo(0, 0);
But in my real scenario parent wrapper also had overflow: hidden; which prevented above code from working. So I've used refs
const handleFocus = (num) => {
if (num !== curr) {
setCurr(num);
carouselRef.current.scrollTo(0, 0);
}
};
return (
<div ref={carouselRef}>
<div className="carousel" style={carouselStyles}>
...
</div>
current: {curr}
</div>
);

Prevent focus on Expand More button after content is inserted in React

I need to list out a long name list inside my page while showing all names at first is not desirable.
So I try to add an expand more button on it.
However, using a button will keep the browser focus on that button after it's pressed, left the button position unchanged on the screen while the name was inserted before that button.
On the other hand, using any, not focusable element (eg. div with onclick function) will do the desired behavior but lost the accessibility at all. Making the "button" only clickable but not focusable.
How do I make the button flushed to list bottom like the snippet div block does? Or is there a better choice to expand the existing list?
const myArray = [
'Alex',
'Bob',
'Charlie',
'Dennis',
'Evan',
'Floron',
'Gorgious',
'Harris',
'Ivan',
'Jennis',
'Kurber',
'Lowrance',
]
const ExpandList = (props) => {
const [idx, setIdx] = React.useState(8)
const handleExpand = e => {
setIdx(idx + 1)
}
return <div className='demo'>
<h1>Name List</h1>
{myArray.slice(0,idx).map(
name => <p key={name}>{name}</p>
)}
<div>
<button onClick={handleExpand} children='Button Expand' className='pointer' />
<div onClick={handleExpand} className='pointer'>Div Expand</div>
</div>
</div>
}
ReactDOM.render(<ExpandList/>, document.getElementById('root'))
.demo>p {
display: block;
padding: 20px;
color: #666;
background: #3331;
}
.demo>div>div {
display: flex;
padding: 15px;
margin-left: auto;
color: #666;
background: #3331;
}
.pointer {
cursor: pointer;
}
.pointer:hover {
background-color: #6663;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.14.0/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.14.0/umd/react-dom.production.min.js"></script>
<div id='root' class='demo'>hello</div>

Removing focus from the button in the click handler is probably the most elegant approach: e.target.blur(). It will work on any HTML element, whether it is focusable or not (as with the div in your case).
const myArray = [
'Alex',
'Bob',
'Charlie',
'Dennis',
'Evan',
'Floron',
'Gorgious',
'Harris',
'Ivan',
'Jennis',
'Kurber',
'Lowrance',
]
const ExpandList = (props) => {
const [idx, setIdx] = React.useState(8)
const handleExpand = e => {
e.target.blur()
setIdx(idx + 1)
}
return <div className='demo'>
<h1>Name List</h1>
{myArray.slice(0,idx).map(
name => <p key={name}>{name}</p>
)}
<div>
<button onClick={handleExpand} children='Button Expand' className='pointer' />
<div onClick={handleExpand} className='pointer'>Div Expand</div>
</div>
</div>
}
ReactDOM.render(<ExpandList/>, document.getElementById('root'))
.demo>p {
display: block;
padding: 20px;
color: #666;
background: #3331;
}
.demo>div>div {
display: flex;
padding: 15px;
margin-left: auto;
color: #666;
background: #3331;
}
.pointer {
cursor: pointer;
}
.pointer:hover {
background-color: #6663;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.14.0/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.14.0/umd/react-dom.production.min.js"></script>
<div id='root' class='demo'>hello</div>

Inspired by #MiKo, temporally unmount the button after click and set a timeout to add it back seems to do the work. Since browser lose the focus on original expand button, this will keep content flush down without focusing the original button:
const ExpandList = (props) => {
const [idx, setIdx] = React.useState(8)
const [showBtn, setShowBtn] = React.useState(true)
const handleExpand = e => {
setShowBtn(false)
setIdx(idx + 1)
setTimeout(() => setShowBtn(true), 10)
}
return <div className='demo'>
<h1>Name List</h1>
{myArray.slice(0,idx).map(
name => <p key={name}>{name}</p>
)}
{showBtn?
<div>
<button onClick={handleExpand} children='Button Expand' className='pointer' />
<div onClick={handleExpand} className='pointer'>Div Expand</div>
</div> :
<div></div>
}
</div>
}
But I'm still looking a method that doesn't need to 'unmount' a thing which should be there all time.

How to find the index of an event target's parent node in JS?

When the page loads, an array is made that holds a group of divs and is used as a global variable catGroup. Each div has a button as a child, and when clicked, the target is saved as a global variable targ. What I'm trying to do is determine the index of the button's parent node every time it is clicked. I haven't been able to find a way to make this happen. Any help is appreciated.
i = catGroup.findIndex(node => node == targ.parentNode);

Wrap an element around all <div>s then register it to the click event:
document.querySelector('main').onclick = clickHandler;
Get the <div> of the button clicked by user:
const clicked = e.target;
const act = clicked.parentElement;
Collect all <div> that are direct descendants of <main>:
const divs = [...this.querySelectorAll('main > div')];
Remove '.active' from all <div> and then add .active to the parent <div> of clicked button:
divs.forEach(d => d.classList.remove('active'));
act.classList.add('active');
Filter the array of divs and return it's index:
idx = divs.flatMap((d, i) => d.className === 'active' ? i : []);
idx = divs.findIndex(d => d === act);
// As Peter Seliger suggested -- I brain farted
const main = document.querySelector('main');
main.onclick = getIndex;
function getIndex(e) {
let idx;
const clicked = e.target;
const divs = [...this.querySelectorAll('main > div')];
if (clicked.matches('[type="button"]') || clicked.matches('button')) {
const act = clicked.parentElement;
divs.forEach(d => d.classList.remove('active'));
act.classList.add('active');
idx = divs.findIndex(d => d === act);
}
document.querySelector('section').textContent = idx;
}
html {
font: 2ch/1 Consolas;
}
body {
position: relative;
height: 100vh
}
main {
padding: 5px 20px 10px;
}
section {
position: fixed;
top: 0;
left: 50%;
font-size: 5rem;
}
div {
width: 8.5ch;
text-align: center;
}
[type='button'], button {
display: block;
width: 10ch;
height: 3ch;
cursor: pointer;
}
<main>
<section></section>
<div><input type='button' value='0'></div>
<div><input type='button' value='1'></div>
<div><input type='button' value='2'></div>
<div><button>3</button></div>
<div><input type='button' value='4'></div>
<div><button>5</button></div>
<div><input type='button' value='6'></div>
<div><input type='button' value='7'></div>
<div><button>8</button></div>
<div><input type='button' value='9'></div>
</main>

This worked for me in a mouseover event. That's how I did it in my case:
onMouseOver={(e) => { const idx = Array.from(e.target.parentNode.children).indexOf(e.target); }}