keyCode is a deprecated property of keyboard events that returns a numeric code representing the key that was pressed. For example, 13 for Enter, 27 for Escape, and 65 for the letter A. While still supported in browsers, it's recommended to use event.key or event.code instead.

keyCode was deprecated because it's hard to read (numeric codes vs. names), inconsistent across browsers, doesn't support international keyboards well, and can't distinguish between left and right modifier keys. The modern event.key and event.code properties solve these problems.

keyCode (deprecated) returns numeric values like 13 or 65. event.key returns the actual character or key name like 'Enter' or 'a'. event.code returns the physical key location like 'Enter' or 'KeyA', which doesn't change with keyboard layout.

Use event.key to detect arrow keys. For example: if (e.key === 'ArrowUp') { }. The arrow key values are 'ArrowUp', 'ArrowDown', 'ArrowLeft', and 'ArrowRight'. Legacy keyCodes are 37-40.

For common keys, yes, but there were historical inconsistencies, especially for special keys and international keyboards. This is one reason keyCode was deprecated. The modern event.key and event.code properties are standardized and consistent across all modern browsers.

Use the boolean properties e.ctrlKey, e.altKey, e.shiftKey, and e.metaKey to check if modifier keys are pressed during any keyboard event. For example: if (e.ctrlKey && e.key === 's') { } detects Ctrl+S.

Use event.key for most cases like text input and form handling. Use event.code for game controls or when you need to detect physical key position regardless of keyboard layout (like WASD keys).

Call e.preventDefault() in your keydown event handler when arrow keys are detected. For example: if (e.key.startsWith('Arrow')) { e.preventDefault(); }. Only do this when necessary, as users expect arrow keys to scroll.