function constantcase( str ) {
	str = replace( str, RE_SPECIAL, ' ' );
	str = replace( str, RE_CAMEL, '$1 $2' );
	str = trim( str );
	str = replace( str, RE_WHITESPACE, '_' );
	return uppercase( str );
}
Converts a string to constant case.

@param {string} str - string to convert
@returns {string} constant-cased string

@example
var str = constantcase( 'beep' );
// returns 'BEEP'

@example
var str = constantcase( 'beep boop' );
// returns 'BEEP_BOOP'

@example
var str = constantcase( 'isMobile' );
// returns 'IS_MOBILE'

@example
var str = constantcase( 'Hello World!' );
// returns 'HELLO_WORLD'