The KeyboardEvent.shiftKey read-only property is a boolean value that indicates if the shift key was pressed (true) or not (false) when the event occurred.
The pressing of the shift key may change the key of the event too. For example, pressing B generates key: "b", while simultaneously pressing Shift generates key: "B".
A boolean value.
<p>
Press any character key, with or without holding down the SHIFT key.<br />
You can also use the SHIFT key together with the ALT key.
</p>
<pre id="output"></pre>const output = document.getElementById("output");
function showChar(e) {
output.textContent = `Key KeyDown: "${e.key}"
SHIFT key KeyDown: ${e.shiftKey}
`;
}
document.addEventListener("keydown", showChar);