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47 lines
1.3 KiB
47 lines
1.3 KiB
'use strict'; |
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var GetIntrinsic = require('get-intrinsic'); |
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var IsInteger = require('./IsInteger'); |
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var Type = require('./Type'); |
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var MAX_SAFE_INTEGER = require('../helpers/maxSafeInteger'); |
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var isLeadingSurrogate = require('../helpers/isLeadingSurrogate'); |
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var isTrailingSurrogate = require('../helpers/isTrailingSurrogate'); |
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var $TypeError = GetIntrinsic('%TypeError%'); |
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var $charCodeAt = require('call-bind/callBound')('String.prototype.charCodeAt'); |
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// https://ecma-international.org/ecma-262/6.0/#sec-advancestringindex |
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module.exports = function AdvanceStringIndex(S, index, unicode) { |
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if (Type(S) !== 'String') { |
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throw new $TypeError('Assertion failed: `S` must be a String'); |
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} |
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if (!IsInteger(index) || index < 0 || index > MAX_SAFE_INTEGER) { |
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throw new $TypeError('Assertion failed: `length` must be an integer >= 0 and <= 2**53'); |
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} |
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if (Type(unicode) !== 'Boolean') { |
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throw new $TypeError('Assertion failed: `unicode` must be a Boolean'); |
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} |
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if (!unicode) { |
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return index + 1; |
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} |
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var length = S.length; |
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if ((index + 1) >= length) { |
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return index + 1; |
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} |
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var first = $charCodeAt(S, index); |
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if (!isLeadingSurrogate(first)) { |
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return index + 1; |
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} |
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var second = $charCodeAt(S, index + 1); |
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if (!isTrailingSurrogate(second)) { |
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return index + 1; |
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} |
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return index + 2; |
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};
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