using functions to `case` match in `switch` statements

gistfile1.md

the main caveat is that each case function will be executed until a match is found, however, this would not be any different from doing the same thing using if/else.

note: i am not advocating this method, it's just something i've never seen done before and thought it was interesting enough to share.

more_goodera_example.js

// yes there are more key codes than this, it's just an example though, so chillax...
;!function() {
// 112 == F1, 123 == F12
	function f_key( kc ) { 
		return ( kc >= 112 && kc <= 123 ) ? kc : false; 
	}
// 65 == 'A', 90 == 'Z', 32 == ' ' <= space character
	function letter( kc ) { 
		return ( kc >=  65 && kc <=  90 ) || kc == 32 ? kc : false; 
	}
// pg up, pg down, end, home, left, up, right, down, tab
	function navigation( kc ) {
		return ( kc >=  33 && kc <=  40 ) || kc ==  9 ? kc : false; 
	}
// 48 == 0, 57 == 9 | NUMBER PAD: 96 == 0, 105 == 9 
	function number( kc ) { 
		return ( kc >=  48 && kc <=  57 ) || ( kc >= 96 && kc <= 105 ) ? kc : false; 
	}
	
	document.addEventListener( 'keydown', function( evt ) {
		var kc = evt.keyCode, msg;
		switch ( kc ) {
			case letter( kc )     : msg = 'a letter';        break;
			case number( kc )     : msg = 'a number';        break;
			case navigation( kc ) : msg = 'a navigation';    break;
			case f_key( kc )      : msg = 'a function key';  break;
			default               : msg = 'some other key';  break;
		}
		console.log( msg + ' was pressed, not telling which one though.' );
	}, false );
}();

simple__yet_useless__example.js

;!function() {
// it's important to return the actual value in the `switch` so we get the correct `case` match or the `switch` will only match `default`
	function lt( val, bound ) { return val <= bound ? val : false; }
	function within( val, lower_bound, upper_bound ) { return val >= lower_bound && val <= upper_bound ? val : false; }
	
	var msg, val = 17;

	switch ( val ) {
		case lt( val,  5 ) : msg = ' is less than or equal to 5.';  break;
		case lt( val, 10 ) : msg = ' is less than or equal to 10.'; break;
		case lt( val, 15 ) : msg = ' is less than or equal to 15.'; break;
		case lt( val, 20 ) : msg = ' is less than or equal to 20.'; break;
		case lt( val, 25 ) : msg = ' is less than or equal to 25.'; break;
		default            : msg = ' is greater than 25.';          break;
	}

	console.log( val, msg );

	switch ( val ) {
		case within( val,  0,  5 ) : msg = ' is within the range of 0-5.';  break;
		case within( val,  6, 10 ) : msg = ' is within the range of 6-10.'; break;
		case within( val, 11, 15 ) : msg = ' is within the range of 11-15.'; break;
		case within( val, 16, 20 ) : msg = ' is within the range of 16-20.'; break;
		case within( val, 21, 25 ) : msg = ' is within the range of 21-25.'; break;
		default                    : msg = ' is not in a valid range.';      break;
	}
	
	console.log( val, msg );
}();