detect when an element is ready
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/419640/887637/onElementReady.js
// This code from: https://gist.githubusercontent.com/zachhardesty7/ea61364567ce66b94edb81f922efecef/raw/c23ba499828992d632266194384c72ff28dfad6e/onElementReady.js
// ==UserScript==
// @name Library | onElementReady ES6
// @namespace de.sidneys.userscripts
// @homepage https://gist.githubusercontent.com/zachhardesty7/b19c33e4b2cec8861d55df10be0ce162/raw/
// @version 0.6.0
// @description Detect any new DOM Element by its CSS Selector, then trigger a function. Includes Promise- & Callback interface. Based on ES6 MutationObserver. Ships legacy waitForKeyElements interface, too.
// @author sidneys
// @icon https://i.imgur.com/nmbtzlX.png
// @include *://*/*
// ==/UserScript==
/**
* ESLint
* @exports
*/
/* exported onElementReady */
/* exported waitForKeyElements */
/**
* @private
*
* Query for new DOM nodes matching a specified selector.
*
* @param {String} selector - CSS Selector
* @param {{ findFirst: boolean, findOnce: boolean }} options - Stop querying after first successful pass, find each el only a single time
* @param {function=} callback - Callback
*/
let queryForElements = (selector, options = { findFirst: false, findOnce: true }, callback) => {
// Remember already-found elements via this attribute
const attributeName = 'was-queried'
// Search for elements by selector
let elementList = document.querySelectorAll(selector) || []
elementList.forEach((element) => {
if (element.hasAttribute(attributeName)) { return }
element.setAttribute(attributeName, 'true')
callback(element)
// run reset after 2 seconds
if (!options.findOnce) {
setTimeout(() => {
element.removeAttribute(attributeName)
}, 2000)
}
})
}
/**
* @public
*
* Wait for Elements with a given CSS selector to enter the DOM.
* Returns a Promise resolving with new Elements, and triggers a callback for every Element.
*
* @param {String} selector - CSS Selector
* @param {{ findFirst: boolean, findOnce: boolean }} options - Stop querying after first successful pass, find each el only a single time
* @param {function=} callback - Callback with Element
* @returns {Promise<Element>} - Resolves with Element
*/
let onElementReady = (selector, options = { findFirst: false, findOnce: true }, callback = () => {}) => {
return new Promise((resolve) => {
// Initial Query
queryForElements(selector, options, (element) => {
resolve(element)
callback(element)
})
// Continuous Query
const observer = new MutationObserver(() => {
// DOM Changes detected
queryForElements(selector, options, (element) => {
resolve(element)
callback(element)
})
if (options.findFirst) { observer.disconnect() }
})
// Observe DOM Changes
observer.observe(document.documentElement, {
attributes: false,
childList: true,
subtree: true
})
})
}
/**
* @public
* @deprecated
*
* waitForKeyElements Polyfill
*
* @param {String} selector - CSS selector of elements to search / monitor ('.comment')
* @param {function} callback - Callback executed on element detection (called with element as argument)
* @param {{ findFirst: boolean, findOnce: boolean }} options - Stop querying after first successful pass, find each el only a single time
* @returns {Promise<Element>} - Element
*/
let waitForKeyElements = (selector, callback, options) => onElementReady(selector, options, callback)