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userscripts-core-library

Core library to handle webpages dom with userscripts from document-start

当前为 2023-09-24 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.greasyfork.icu/scripts/476017/1255617/userscripts-core-library.js 

// ==UserScript==
// @name        userscripts-core-library
// @version     0.1.0
// @author      lucianjp
// @description Core library to handle webpages dom with userscripts from document-start
// ==/UserScript==

const core = {
  ready: (callback) =>
    document.readyState !== "loading"
      ? callback()
      : document.addEventListener("DOMContentLoaded", callback),
  addStyle: (aCss) => {
    let head = document.getElementsByTagName("head")[0];
    if (!head) {
      console.error("Head element not found. Cannot add style.");
      return null;
    }

    let style = document.createElement("style");
    style.setAttribute("type", "text/css");
    style.textContent = aCss;
    head.appendChild(style);
    return style;
  },
  observe: (observableCollection, continuous = false) => {
    const observables = Array.from(observableCollection.entries()).filter(
      ([_, observable]) => !observable.currentValue
    );

    const observer = new MutationObserver(function (mutations) {
      for (var i = mutations.length - 1; i >= 0; i--) {
        const mutation = mutations[i];
        const addedNodesLength = mutation.addedNodes.length;
        if (addedNodesLength > 0) {
          for (var j = addedNodesLength - 1; j >= 0; j--) {
            const $node = mutation.addedNodes[j];
            if ($node && $node.nodeType === 1) {
              let observablesLength = observables.length;
              for (let k = observablesLength - 1; k >= 0; k--) {
                const [_, observable] = observables[k];

                if (observable.test($node)) {
                  observable.set($node);
                  const last = observables.pop();
                  if (k < observablesLength - 1) observables[k] = last;
                  observablesLength = observablesLength - 1;
                  break;
                }
              }
            }
          }

          if (observables.length === 0 && !continuous) {
            observer.disconnect();
            return;
          }
        }
      }
    });

    observer.observe(document, { childList: true, subtree: true });

    if (!continuous) core.ready(() => observer.disconnect());

    return observer;
  },
};

class Observable {
  constructor(lookup, test) {
    this.value = undefined;
    this.callbacks = [];
    this.lookup = lookup;
    this.test = test;

    if (typeof lookup === "function") {
      this.value = lookup();
    }
  }

  set(newValue) {
    this.value = newValue;
    this.executeCallbacks(this.value);
  }

  then(callback) {
    if (typeof callback === "function") {
      this.callbacks.push(callback);
      if (this.value) callback(this.value);
    }
    return this;
  }

  executeCallbacks(value) {
    this.callbacks.forEach((callback) => callback(value));
  }

  get currentValue() {
    return this.value;
  }
}

class ObservableCollection extends Map {
  constructor() {
    super();
  }

  add(name, observable) {
    this.set(name, observable);
    return observable;
  }
}