1var toInteger = require('./_to-integer');
2var defined = require('./_defined');
3// true  -> String#at
4// false -> String#codePointAt
5module.exports = function (TO_STRING) {
6  return function (that, pos) {
7    var s = String(defined(that));
8    var i = toInteger(pos);
9    var l = s.length;
10    var a, b;
11    if (i < 0 || i >= l) return TO_STRING ? '' : undefined;
12    a = s.charCodeAt(i);
13    return a < 0xd800 || a > 0xdbff || i + 1 === l || (b = s.charCodeAt(i + 1)) < 0xdc00 || b > 0xdfff
14      ? TO_STRING ? s.charAt(i) : a
15      : TO_STRING ? s.slice(i, i + 2) : (a - 0xd800 << 10) + (b - 0xdc00) + 0x10000;
16  };
17};
18