fix-reddit-hot.js

// ==UserScript==
// @name        Hot Reddit Fix
// @namespace   Rapptz.Misc
// @author      Rapptz
// @description Makes the reddit homepage Hot sort
// @include     http://*.reddit.com/*
// @include     https://*.reddit.com/*
// @version     1.0
// @run-at      document-start
// ==/UserScript==

let url = new URL(window.location);

if(url.pathname == '/') {
  // raw homepage, so just redirect
  window.location.replace(`${url.href}hot`);
}

function replaceButton() {
  // replace best button with /best
  let homepage = `${url.protocol}//${url.hostname}/`;

  for(let node of document.querySelectorAll(".tabmenu > li > a")) {
    if(node.href === homepage) {
      node.href = homepage + 'best';
    }
  }
}

window.addEventListener("load", replaceButton);