const box = document.querySelector("#resizable");

const ro = new ResizeObserver((entries) => {
  for (const entry of entries) {
    console.log("contentRect:", entry.contentRect.width, entry.contentRect.height);
    console.log("borderBoxSize:", entry.borderBoxSize[0].inlineSize, "x", entry.borderBoxSize[0].blockSize);
    if (entry.devicePixelContentBoxSize[0])
      console.log("device pixels:", entry.devicePixelContentBoxSize[0].inlineSize);
  }
});

// "content-box" | "border-box" | "device-pixel-content-box"
ro.observe(box, { box: "content-box" });

// Later: ro.unobserve(box); ro.disconnect();

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