☰

setMutationHandler

MutationObserver wrapper to wait for the specified CSS selector

当前为 2017-02-10 提交的版本，查看 最新版本。

此脚本不应直接安装。它是供其他脚本使用的外部库，要使用该库请加入元指令 // @require https://update.cn-greasyfork.org/scripts/12228/174269/setMutationHandler.js 

/* EXAMPLE:

	setMutationHandler(document, '.container p.some-child', function(nodes) {
		// single node:
		nodes[0].remove();

		// or multiple nodes:
		nodes.forEach(node => node.style.display = 'none');

		// disconnect the observer, this is useful for one-time jobs
		return false;
	});
*/

// ==UserScript==
// @name          setMutationHandler
// @description   MutationObserver wrapper to wait for the specified CSS selector
// @namespace     wOxxOm.scripts
// @author        wOxxOm
// @grant         none
// @version       2.1.0
// ==/UserScript==

function setMutationHandler(baseNode, selector, cb, options) {
	baseNode = baseNode || document;
	var ob;
	if (/^#[\w\d-]+$/.test(selector)) {
		selector = selector.substr(1);
		ob = new MutationObserver(MOhandlerForId);
	} else {
		ob = new MutationObserver(MOhandler);
	}
	ob.observe(baseNode, options || {subtree:true, childList:true});
	return ob;

	function MOhandler(mutations, observer) {
		if (mutations.length > 100 && !document.querySelector(selector))
			return;
		var found = [];
		for (var i=0, m; (m = mutations[i++]); ) {
			switch (m.type) {
				case 'childList':
					var nodes = m.addedNodes, nl = nodes.length;
					var textNodesOnly = true;
					for (var j=0; j < nl; j++) {
						var n = nodes[j];
						textNodesOnly &= n.nodeType == 3; // TEXT_NODE
						if (n.nodeType != 1) // ELEMENT_NODE
							continue;
						if (n.matches(selector))
							found.push(n);
						else if (n.querySelector(selector)) {
							n = n.querySelectorAll(selector);
							if (n.length < 1000)
								found.push.apply(found, n);
							else
								found = found.concat(found.slice.call(n));
						}
					}
					if (textNodesOnly && m.target.matches(selector))
						found.push(m.target);
					break;
				case 'attributes':
					if (m.target.matches(selector))
						found.push(m.target);
					break;
				case 'characterData':
					if (m.target.parentNode && m.target.parentNode.matches(selector))
						found.push(m.target.parentNode);
					break;
			}
		}
		if (!found.length)
			return;
		if (cb.call(ob, found) === false)
			ob.disconnect();
	}

	function MOhandlerForId(mutations, observer) {
		var el = document.getElementById(selector);
		if (!el || !baseNode.contains(el))
			return;
		if (cb.call(ob, [el]) === false)
			ob.disconnect();
	}
}