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waitForElement

Waits for an element using the MutationObserver API

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/528234/1596455/waitForElement.js 

  1. // ==UserScript==
  2. // @name         waitForElement
  3. // @namespace    Violentmonkey Scripts
  4. // @version      2.0
  5. // @description  Waits for an element using the MutationObserver API
  6. // @author       maanimis
  7. // @grant        none
  8. // ==/UserScript==
  9.  
  10. /**
  11.  * Waits for a element of a given selector.
  12.  *
  13.  * @param {string} selector
  14.  * @returns {Promise<HTMLElement>}
  15.  */
  16.  function waitForElement(selector) {
  17.   return new Promise((resolve) => {
  18.     // Ensure <body> is ready
  19.     function ensureBodyReady(callback) {
  20.       if (document.body) return callback();
  21.       requestAnimationFrame(() => ensureBodyReady(callback));
  22.     }
  23.  
  24.     ensureBodyReady(() => {
  25.       const ELEMENT = document.querySelector(selector);
  26.       if (ELEMENT) return resolve(ELEMENT);
  27.  
  28.       console.log("can't find element for selector:", selector, "waiting...");
  29.  
  30.       const observer = new MutationObserver(() => {
  31.         const ELEMENT = document.querySelector(selector);
  32.         if (ELEMENT) {
  33.           console.log("element found!!");
  34.           resolve(ELEMENT);
  35.           observer.disconnect();
  36.         }
  37.       });
  38.  
  39.       observer.observe(document.body, {
  40.         childList: true,
  41.         subtree: true,
  42.       });
  43.     });
  44.   });
  45. }