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27 lines
818 B
JavaScript
27 lines
818 B
JavaScript
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// Based on: https://github.com/mathiasbynens/String.prototype.codePointAt
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// Thanks @mathiasbynens !
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"use strict";
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var toInteger = require("../../../number/to-integer")
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, validValue = require("../../../object/valid-value");
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module.exports = function (pos) {
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var str = String(validValue(this)), length = str.length, first, second;
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pos = toInteger(pos);
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// Account for out-of-bounds indices:
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if (pos < 0 || pos >= length) return undefined;
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// Get the first code unit
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first = str.charCodeAt(pos);
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if (first >= 0xd800 && first <= 0xdbff && length > pos + 1) {
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second = str.charCodeAt(pos + 1);
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if (second >= 0xdc00 && second <= 0xdfff) {
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// http://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae
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return (first - 0xd800) * 0x400 + second - 0xdc00 + 0x10000;
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}
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}
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return first;
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};
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