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// Based on: https://github.com/mathiasbynens/String.prototype.at
// Thanks @mathiasbynens !
'use strict';
var toInteger = require('../../number/to-integer')
, validValue = require('../../object/valid-value');
module.exports = function (pos) {
var str = String(validValue(this)), size = str.length
, cuFirst, cuSecond, nextPos, len;
pos = toInteger(pos);
// Account for out-of-bounds indices
// The odd lower bound is because the ToInteger operation is
// going to round `n` to `0` for `-1 < n <= 0`.
if (pos <= -1 || pos >= size) return '';
// Second half of `ToInteger`
pos = pos | 0;
// Get the first code unit and code unit value
cuFirst = str.charCodeAt(pos);
nextPos = pos + 1;
len = 1;
if ( // check if it’s the start of a surrogate pair
(cuFirst >= 0xD800) && (cuFirst <= 0xDBFF) && // high surrogate
(size > nextPos) // there is a next code unit
) {
cuSecond = str.charCodeAt(nextPos);
if (cuSecond >= 0xDC00 && cuSecond <= 0xDFFF) len = 2; // low surrogate
}
return str.slice(pos, pos + len);
};
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