JSFiddle - React, Tailwind, and code Playground

HTML

<div id="demo"></div>

JavaScript

var array = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
    index = 8,
    n = 3;

var result = [];

for (var i = index - n, len = array.length; i <= index + n; i++) {
    result.push(array[(i + len) % len]);
}

document.querySelector("#demo").innerHTML = result.join(", ")