show-net-diff-in-github-prs.js

// ==UserScript==
// @name         NetDiff
// @namespace    http://tampermonkey.net/
// @version      1.0
// @description  Show net diff in Github PRs
// @author       Abhijit Hota (abhijithota.me)
// @match        https://github.com/*/*/pull/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

	const diff = document.getElementById('diffstat');
	const additions = diff.children[0].innerText.replaceAll(/[^\d]/g, '');
	const deletions = diff.children[1].innerText.replaceAll(/[^\d]/g, '');
	const netDiff = parseInt(additions) - parseInt(deletions);

	const newSpan = document.createElement('span');

	newSpan.innerText = `(Net Diff: ${netDiff > 0 ? "+" : ""}${netDiff})`;
	newSpan.style.marginLeft = '0.5rem';

	diff.appendChild(newSpan);
})();