What is a storage event and its event handler

A storage event is an event that is triggered when a storage area (localStorage or sessionStorage) is changed in the browser. This event is triggered on the window object and can be used to detect when data is added, removed, or modified in the storage area.

The event handler for a storage event is a function that is called when the storage event is triggered. This function can be used to detect when the storage area has been changed and take appropriate action.

Example

Here is an example of a storage event handler in Javascript:

window.addEventListener('storage', function(e) {
  // Check the key of the storage item that was changed
  if (e.key === 'myData') {
    // Get the new value of the storage item
    var newValue = e.newValue;
    // Do something with the new value
  }
});

In this example, the storage event handler is listening for changes to the storage item with the key of myData. When the storage item is changed, the event handler will be called and the new value of the storage item can be accessed via the e.newValue property.