documentattachEventonreadystatechange
Document.attachEvent onreadystatechange refers to a legacy Internet Explorer mechanism for binding a handler to the document’s onreadystatechange event. It was used in older IE versions (approximately IE 5–8) as a non-standard alternative to the standard addEventListener approach.
The onreadystatechange event fires when the document’s readyState changes. The common states are loading, interactive, and
Compatibility and deprecation: attachEvent is non-standard and is not supported in modern browsers. It has different
document.attachEvent("onreadystatechange", function () {
if (document.readyState === "complete") {
}
});
Today, developers should avoid document.attachEvent and onreadystatechange bindings in favor of standards-compliant patterns, ensuring cross-browser compatibility