code: function getAlias ( chars, i ) {
  	let alias = '';
  	let base = 54;
  
  	i++;
  	do {
  		i--;
  		alias += chars[ i % base ];
  		i = Math.floor( i / base );
  		base = 64;
  	} while ( i > 0 );
  
  	return alias;
  }
docs: adapted from https://github.com/mishoo/UglifyJS2/blob/master/lib/scope.js