Referenceerror: resizeobserver is not defined

When encountering the error “ReferenceError: ResizeObserver is not defined”, it means that the ResizeObserver API is not available in the current browser or environment.

The ResizeObserver API is used to monitor changes in the size of DOM elements. It provides a way to be notified when an element’s size changes, allowing developers to perform certain actions based on those changes.

To resolve this error, you can check for browser support for the ResizeObserver API before using it. Here’s an example of how you can do this:

    if (typeof ResizeObserver === 'undefined') {
      // ResizeObserver API is not supported
      // Handle accordingly (e.g., use a polyfill or fallback solution)
    } else {
      // ResizeObserver API is supported
      // Use it as intended
      const resizeObserver = new ResizeObserver((entries) => {
        // Callback function executed when an element is resized
        entries.forEach(entry => {
          // Access entry.target to get the observed element
          // Perform actions based on the size changes
        });
      });

      const elementToObserve = document.querySelector('.element-to-observe');
      resizeObserver.observe(elementToObserve);
    }
  

In the example above, the first condition checks if the ResizeObserver is undefined, indicating that it is not available. In this case, you can handle the situation by using a polyfill or a fallback solution.

If the ResizeObserver is defined, an instance of it is created with a callback function. This callback function is executed whenever the observed element is resized. You can access the observed element through the entry.target property of each entry in the entries array.

Finally, an element is selected to observe with the ResizeObserver using the .observe() method. Whenever this element’s size changes, the callback function will be triggered.