JSFiddle - React, Tailwind, and code Playground
by LeD4eG
HTML
<html>
<head>
<title>Simple func</title>
</head>
<body></body>
</html>
JavaScript
function sumTo(n) {
return (n>0)? n + sumTo(n-1) : n;
}
var number = parseInt(prompt("Введите число", ''));
alert(sumTo(number));