Set a tab size for code on the web

tabSize.js

// ==UserScript==
// @name         Tab Size
// @namespace    http://tampermonkey.net/
// @version      0.3
// @description  Set the tab size in code views
// @author       Evan Yamanishi
// @match        *://*/*
// @grant        none
// @run-at      document-start
// ==/UserScript==

(function () {
	'use strict';

	// Your chosen tab size. Change this to whatever you want!
	const TAB_SIZE_DEFAULT = 4;

	// The elements that should use this tab size
	const SELECTORS = [
		'.highlight > pre > .line span:first-child:not(:only-child)',
		'.prism-code .token-line > .token',
		'.blob-code-inner',
		'code',
		'pre',
		'tt',
	].join(', ');

	// The list of CSS properties that should have the tab size
	const props = (tabSize) => [
		'-moz-tab-size',
		'-o-tab-size',
		'tab-size',
	].map((prop) => `${prop}: ${tabSize} !important;`).join('\n\t');

	window.setTabSize = (tabSize = TAB_SIZE_DEFAULT) => {
		const ID = 'sh0ji-tab-size';
		const styleElement = document.getElementById(ID) || document.createElement('style');
		styleElement.id = ID;
		styleElement.innerHTML = `${SELECTORS} { ${props(tabSize)} }`;
		document.head.appendChild(styleElement);
	};

    window.setTabSize();
}());