function startcase( str ) {
	if ( !isString( str ) ) {
		throw new TypeError( format( 'invalid argument. Must provide a string. Value: `%s`.', str ) );
	}
	return base( str );
}
Capitalizes the first letter of each word in an input string.

@param {string} str - string to convert
@throws {TypeError} must provide a string
@returns {string} start case string

@example
var str = startcase( 'beep boop foo bar' );
// returns 'Beep Boop Foo Bar'