function altcase( str ) {
	var out = '';
	var i;
	for ( i = 0; i < str.length; i++ ) {
		if ( isEven( i ) ) {
			out += lowercase( str[i] );
		} else {
			out += uppercase( str[i] );
		}
	}
	return out;
}
Converts a string to alternate case.

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

@example
var str = altcase( 'beep' );
// returns 'bEeP'

@example
var str = altcase( 'beep boop' );
// returns 'bEeP BoOp'

@example
var str = altcase( 'isMobile' );
// returns 'iSmObIlE'

@example
var str = altcase( 'Hello World!' );
// returns 'hElLo wOrLd!'