README.me

# resizeObserver

If you want to prevent these errors, the solution depends on what your intended effect is. If you actually intend to have an infinite loop, you just need to defer the resizing code in your ResizeObserver callback to after the browser repaints. You can put it into a requestAnimationFrame callback.

## 1
```js

const divElem = document.querySelector("body > div");

const resizeObserver = new ResizeObserver((entries) => {
  requestAnimationFrame(() => {
    for (const entry of entries) {
      entry.target.style.width = entry.contentBoxSize[0].inlineSize + 10 + "px";
    }
  });
});

resizeObserver.observe(divElem);

window.addEventListener("error", (e) => {
  console.error(e.message);
});
```

If you don't intend to have an infinite loop, you should make sure your resizing code does not trigger the resize observer callback. There are many ways to do this, such as by setting an "expected size" and not resizing if the size is already at that value.
## 2
```js
const divElem = document.querySelector("body > div");
const expectedSizes = new WeakMap();

const resizeObserver = new ResizeObserver((entries) => {
  requestAnimationFrame(() => {
    for (const entry of entries) {
      const expectedSize = expectedSizes.get(entry.target);
      if (entry.contentBoxSize[0].inlineSize === expectedSize) {
        continue;
      }
      const newSize = entry.contentBoxSize[0].inlineSize + 10;
      entry.target.style.width = `${newSize}px`;
      expectedSizes.set(entry.target, newSize);
    }
  });
});

resizeObserver.observe(divElem);

window.addEventListener("error", (e) => {
  console.error(e.message);
});
```

resize-observe.js

const divElem = document.querySelector("body > div");
const expectedSizes = new WeakMap();

const resizeObserver = new ResizeObserver((entries) => {
  requestAnimationFrame(() => {
    for (const entry of entries) {
      const expectedSize = expectedSizes.get(entry.target);
      if (entry.contentBoxSize[0].inlineSize === expectedSize) {
        continue;
      }
      const newSize = entry.contentBoxSize[0].inlineSize + 10;
      entry.target.style.width = `${newSize}px`;
      expectedSizes.set(entry.target, newSize);
    }
  });
});

resizeObserver.observe(divElem);

window.addEventListener("error", (e) => {
  console.error(e.message);
});

resizeObserver.js

const divElem = document.querySelector("body > div");

const resizeObserver = new ResizeObserver((entries) => {
  requestAnimationFrame(() => {
    for (const entry of entries) {
      entry.target.style.width = entry.contentBoxSize[0].inlineSize + 10 + "px";
    }
  });
});

resizeObserver.observe(divElem);

window.addEventListener("error", (e) => {
  console.error(e.message);
});