var curElement = document.activeElementdocument.activeElement returns the currently focused element, that is, the element that will get keystroke events if the user types any. This attribute is read only.
Often this will return an <input> or <textarea> object, if it has the text selection at the time. If so, you can get more detail by using the element's selectionStart and selectionEnd properties. Other times the focused element might be a <select> element (menu) or an <input> element, of type button, checkbox or radio.
Note: On Mac, elements that aren't text input elements tend not to get focus assigned to them.
Typically a user can press the tab key to move the focus around the page among focusable elements, and use the space bar to activate it (press a button, choose a radio).
Do not confuse focus with a selection over the document, consisting mostly of static text nodes. See window.getSelection() for that.
When there is no selection, the active element is the page's <body> or null.