ToggleEvent: oldState property
The oldState read-only property of the ToggleEvent interface is a string representing the state the element is transitioning from.
Value
A string. Possible values are "open" (the popover is going from showing to hidden) or "closed" (the popover going from hidden to shown).
Examples
js
const popover = document.getElementById("mypopover");
// ...
popover.addEventListener("beforetoggle", (event) => {
  if (event.oldState === "open") {
    console.log("Popover is being hidden");
  } else {
    console.log("Popover is being shown");
  }
});
Specifications
| Specification | 
|---|
| HTML Standard # dom-toggleevent-oldstate | 
Browser compatibility
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