function constantcase( str ) {
	if ( !isString( str ) ) {
		throw new TypeError( format( 'invalid argument. Must provide a string. Value: `%s`.', str ) );
	}
	return base( str );
}
Converts a string to constant case.

@param {string} str - string to convert
@throws {TypeError} must provide a string
@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'