mutations

GitHub mutations observer library script

Version vom 21.04.2017. Aktuellste Version

Dieses Skript sollte nicht direkt installiert werden. Es handelt sich hier um eine Bibliothek für andere Skripte, welche über folgenden Befehl in den Metadaten eines Skriptes eingebunden wird // @require https://update.greasyforks.org/scripts/28721/189706/mutations.js

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/* GitHub mutations observer library script v0.2.0
 * Detect changes to various elements and trigger an event
 * This script is meant to be used as a library for GitHub-based userscripts
 * Copyright © 2017 Rob Garrison
 * License: MIT
 */
/* jshint esnext:true, unused:true */
(() => {
	"use strict";

	// prefix for event & document body class name, e.g. "ghmo:container"
	const prefix = "ghmo",
		disableAttr = `data-${prefix}-disable`,
		debounceInterval = 200,
		targets = {
			// pjax container (covers general, repo & gists)
			"[data-pjax-container]": {
				count: 0,
				name: "container"
			},
			// comment preview active
			".js-preview-body": {
				count: 0,
				name: "preview"
			},
			// progressively loaded comments; "# items not shown"
			// example: https://github.com/isaacs/github/issues/18
			".js-discussion": {
				count: 0,
				name: "comments"
			},
			// progressively loaded content (diff files)
			".js-diff-progressive-container, .data.blob-wrapper, .js-diff-load-container": {
				count: 0,
				name: "diff"
			}
		},
		list = Object.keys(targets);

	function fireEvents() {
		list.forEach(selector => {
			if (targets[selector].count > 0) {
				// event => "ghmo:container", "ghmo:comments"
				const event = new Event(prefix + ":" + targets[selector].name);
				document.dispatchEvent(event);
			}
			targets[selector].count = 0;
		});
	}

	// prevent error when library is loaded at document-start & no body exists
	document.addEventListener("DOMContentLoaded", () => {
		const container = document.querySelector("body");
		let timer;
		// prevent script from installing more than once
		if (container && !container.classList.contains(prefix + "-enabled")) {
			container.classList.add(prefix + "-enabled");

			// bound to document.body... this may be bad for performance
			// http://stackoverflow.com/a/39332340/145346
			new MutationObserver(mutations => {
				clearTimeout(timer);
				/* document.body attribute used to disable updates; it *should not*
				 * be used regularly as multiple scripts may enable or disable the
				 * observers at inappropriate times. It is best that each script handles
				 * the mutation events triggered by this library on its own
				 */
				if (container.getAttribute(disableAttr)) {
					return;
				}
				let mindx, target, lindx,
					llen = list.length,
					mlen = mutations.length;
				// avoiding use of forEach loops for performance reasons
				for (mindx = 0; mindx < mlen; mindx++) {
					target = mutations[mindx].target;
					if (target) {
						for (lindx = 0; lindx < llen; lindx++) {
							if (target.matches(list[lindx])) {
								targets[list[lindx]].count++;
							}
						}
					}
					timer = setTimeout(() => {
						fireEvents();
					}, debounceInterval);
				}
			}).observe(container, {
				childList: true,
				subtree: true
			});

		}
	});

})();