Additional list toolbar button for StackOverflow editor windows (note: as an answer to the following question: http://softwarerecs.stackexchange.com/q/2833/583)

so-list.user.js

// ==UserScript==
// @name           StackOverflow List Button
// @description    Additional list toolbar button for StackOverflow editor windows
// @version        1.0
//
// @match          *://stackoverflow.com/*
// @match          *://meta.stackoverflow.com/*
// @match          *://pt.stackoverflow.com/*
//
// @match          *://serverfault.com/*
// @match          *://superuser.com/*
// @match          *://askubuntu.com/*
// @match          *://stackapps.com/*
// @match          *://mathoverflow.net/*
//
// @match          *://discuss.area51.stackexchange.com/*
// @match          *://*.stackexchange.com/*
//
// @author         ComFreek <http://stackoverflow.com/users/603003/comfreek>
// @license        The same as all contributions on the StackExchange network: http://creativecommons.org/licenses/by-sa/3.0/
// ==/UserScript==
 
(function () {
	"use strict";
 
	function listify(textarea) {
		var str = textarea.value;
		var selection = str.substring(textarea.selectionStart, textarea.selectionEnd);
 
		selection = "- " + selection.split("\n").join("\n- ");
		textarea.value = str.substr(0, textarea.selectionStart) + selection + str.substr(textarea.selectionEnd);
	}
	
	function provideButton() {
		var listifyBtn = document.createElement("button");
		listifyBtn.setAttribute("type", "button");
		listifyBtn.appendChild(document.createTextNode("Listify!"));
 
		var clickEvtHandler = function () {
			listify(this.parentNode.querySelector("textarea"));
		};
 
		// insert our button before the toolbar
		// inserting it as a toolbar button similar to the ones already provided
		// by the editor would require too much work and time
		var editorBtnBars = document.querySelectorAll(".wmd-button-bar");
 
		for (var i=0, len=editorBtnBars.length; i<len; i++) {
			// Take the original listifyBtn only in the first round
			var newElem = listifyBtn;
			if (i > 0) {
				var newElem = listifyBtn.cloneNode(true);
			}
			
			newElem.addEventListener("click", clickEvtHandler);
			editorBtnBars[i].parentNode.insertBefore(newElem, editorBtnBars[i]);
		}
	}
	provideButton();
})();