function last( str, n ) {
	var len;
	var out;
	var ch1;
	var ch2;
	var cnt;
	var i;
	len = str.length;
	out = '';
	cnt = 0;
	if ( str === '' || n === 0 ) {
		return '';
	}
	if ( n === 1 ) {
		str = str.substring( len-2, len );
		if ( RE_UTF16_SURROGATE_PAIR.test( str ) ) {
			return str;
		}
		return str[1];
	}

	// Process the string backwards one Unicode code unit at a time and count UTF-16 surrogate pairs as a single Unicode code point...
	for ( i = len-1; i >= 0; i-- ) {
		ch1 = str[ i ];
		out = ch1 + out;
		cnt += 1;

		// Check for a low UTF-16 surrogate...
		if ( RE_UTF16_LOW_SURROGATE.test( ch1 ) ) {
			// Check for an unpaired surrogate at the start of the input string...
			if ( i === 0 ) {
				// We found an unpaired surrogate...
				break;
			}
			// Check whether the low surrogate is paired with a high surrogate...
			ch2 = str[ i-1 ];
			if ( RE_UTF16_HIGH_SURROGATE.test( ch2 ) ) {
				// We found a surrogate pair:
				out = ch2 + out;
				i -= 1; // decrement the index to process the next code unit
			}
		}
		// Check whether we've found the desired number of code points...
		if ( cnt === n ) {
			break;
		}
	}
	return out;
}
Returns the last `n` Unicode code points of a string.

@param {string} str - input string
@param {NonNegativeInteger} n - number of Unicode code points to return
@returns {string} output string

@example
var out = last( 'Hello World', 1 );
// returns 'd'

@example
var out = last( 'ASCII', 2 );
// returns 'II'

@example
var out = last( 'JavaScript', 6 );
// returns 'Script'