1 |
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2 | 'use strict';
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3 | module.exports = function (str, pos) {
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4 | if (str === null || str === undefined) {
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5 | throw TypeError();
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6 | }
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7 |
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8 | str = String(str);
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9 |
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10 | var size = str.length;
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11 | var i = pos ? Number(pos) : 0;
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12 |
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13 | if (Number.isNaN(i)) {
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14 | i = 0;
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15 | }
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16 |
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17 | if (i < 0 || i >= size) {
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18 | return undefined;
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19 | }
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20 |
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21 | var first = str.charCodeAt(i);
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22 |
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23 | if (first >= 0xD800 && first <= 0xDBFF && size > i + 1) {
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24 | var second = str.charCodeAt(i + 1);
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25 |
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26 | if (second >= 0xDC00 && second <= 0xDFFF) {
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27 | return ((first - 0xD800) * 0x400) + second - 0xDC00 + 0x10000;
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28 | }
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29 | }
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30 |
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31 | return first;
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32 | };
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