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25 lines
919 B
25 lines
919 B
'use strict'; |
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var $ = require('../internals/export'); |
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var uncurryThis = require('../internals/function-uncurry-this'); |
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var requireObjectCoercible = require('../internals/require-object-coercible'); |
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var toIntegerOrInfinity = require('../internals/to-integer-or-infinity'); |
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var toString = require('../internals/to-string'); |
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var fails = require('../internals/fails'); |
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var charAt = uncurryThis(''.charAt); |
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var FORCED = fails(function () { |
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return '𠮷'.at(-2) !== '\uD842'; |
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}); |
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// `String.prototype.at` method |
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// https://github.com/tc39/proposal-relative-indexing-method |
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$({ target: 'String', proto: true, forced: FORCED }, { |
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at: function at(index) { |
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var S = toString(requireObjectCoercible(this)); |
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var len = S.length; |
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var relativeIndex = toIntegerOrInfinity(index); |
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var k = relativeIndex >= 0 ? relativeIndex : len + relativeIndex; |
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return (k < 0 || k >= len) ? undefined : charAt(S, k); |
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} |
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});
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