Error: Too many re-renders. React limits the number of renders to prevent an infinite loop.

npm init -y >/dev/null
npm install --silent --no-audit --no-fund react@19 react-dom@19 >/dev/null 2>&1
node -e '
const React = require("react");
const { renderToString } = require("react-dom/server");
function Counter() {
  const [count, setCount] = React.useState(0);
  setCount(count + 1);              // state update during render
  return React.createElement("p", null, count);
}
try { renderToString(React.createElement(Counter)); } catch (e) { console.log(e.message); }'

// wrong: setCount runs during render
<button onClick={setCount(count + 1)}>+</button>

// right: React calls the function when the button is clicked
<button onClick={() => setCount(count + 1)}>+</button>

// wrong: setting state from props during render
const [full, setFull] = useState('');
setFull(`${first} ${last}`);

// right: derive it
const full = `${first} ${last}`;