ResizeObserver polyfill

For ancient browsers

目前為 2021-11-07 提交的版本，檢視最新版本。

此腳本不應該直接安裝，它是一個供其他腳本使用的函式庫。欲使用本函式庫，請在腳本 metadata 寫上： // @require https://update.gf.qytechs.cn/scripts/435127/986121/ResizeObserver%20polyfill.js

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換行

class ResizeObserver {
  constructor(callback) {
    this.observables = [];
      // Array of observed elements that looks like this:
      // [{
      //   el: domNode,
      //   size: {height: x, width: y}
      // }]
    this.boundCheck = this.check.bind(this);
    this.boundCheck();
    this.callback = callback;
  }
  
  observe(el) {
    if (this.observables.some((observable) => observable.el === el)) {
      return;
    }
    const newObservable = {
      el: el,
      size: {
        height: el.clientHeight,
        width: el.clientWidth
      }
    }
    this.observables.push(newObservable);
  }
  
  unobserve(el) {
    this.observables = this.observables.filter((obj) => obj.el !== el);
  }
  
  disconnect() {
    this.observables = [];
  }
  
  check() {
    const changedEntries = this.observables.filter((obj) => {
      const currentHeight = obj.el.clientHeight;
      const currentWidth = obj.el.clientWidth;
      if (obj.size.height !== currentHeight || obj.size.width !== currentWidth) {
        obj.size.height = currentHeight;
        obj.size.width = currentWidth;
        return true;
      }
    }).map((obj) => obj.el);
    if (changedEntries.length > 0) {
      this.callback(changedEntries);
    }
    window.requestAnimationFrame(this.boundCheck);
  }
}

const fooDiv = document.getElementById('foo');
const barDiv = document.getElementById('bar');

const resizeObserver = new ResizeObserver((entries) => {
  entries.forEach((entry) => {
    const colors = ['#FFDAE9', '#F9FFEF', '#B5FFE1', '#CBE896', '#ACECF7', '#F2BB05'];
    entry.style.backgroundColor = colors[Math.floor(Math.random() * colors.length)];
  });
});

resizeObserver.observe(fooDiv);

resizeObserver.observe(barDiv);