Error: JSX expressions must have one parent element in ReactJs
Dung Do Tien May 27 2022 314
Hello you guys. I am a newbie in ReactJs and I am learning about the state, I'm trying to create a small app to use useEffect and useState method. I want to know how they work. Like this:
Couter.tsx
import React, { useEffect, useState } from 'react';
export default function CountApp() {
const [counter, setCounter] = useState(0);
useEffect(() => {
if (counter > 0) {
console.log('count: ' + counter);
}
});
return (
<button onClick={() => setCounter(counter + 1)}>Click counter</button>
<h1>Total count: {counter}</h1>
);
} index.tsx
import * as React from 'react';
import { StrictMode } from 'react';
import { createRoot } from 'react-dom/client';
import CountApp from './CountApp';
const rootElement = document.getElementById('root');
const root = createRoot(rootElement);
root.render(
<StrictMode>
<CountApp />
</StrictMode>
); But when I run this app, I get an exception throw JSX expressions must have one parent element.
What is that mean? I installed react version 18.0.8.
I really appreciate any help you can provide.
Have 1 answer(s) found.
- s0
stoyo May 27 2022
The error SX expressions must have one parent element occurs because your
CountAppcomponent returns many HTML tags. This is not alow in React. A component cannot return multiple elements, just like a function can't return multiple values (unless they're wrapped in an array, which is a single value).you can wrap all HTML inside a div, like this:
return ( <div> <button onClick={() => setCounter(counter + 1)}>Click counter</button> <h1>Total count: {counter}</h1> </div> );Or using
<React.Fragment>tag like a container tag, like this:return ( <React.Fragment> <button onClick={() => setCounter(counter + 1)}>Click counter</button> <h1>Total count: {counter}</h1> </React.Fragment> );I hope these solutions will useful to you.
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