var toObject = require('../internals/to-object');
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var floor = Math.floor;
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var replace = ''.replace;
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var SUBSTITUTION_SYMBOLS = /\$([$&'`]|\d{1,2}|<[^>]*>)/g;
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var SUBSTITUTION_SYMBOLS_NO_NAMED = /\$([$&'`]|\d{1,2})/g;
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// `GetSubstitution` abstract operation
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// https://tc39.es/ecma262/#sec-getsubstitution
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module.exports = function (matched, str, position, captures, namedCaptures, replacement) {
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var tailPos = position + matched.length;
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var m = captures.length;
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var symbols = SUBSTITUTION_SYMBOLS_NO_NAMED;
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if (namedCaptures !== undefined) {
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namedCaptures = toObject(namedCaptures);
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symbols = SUBSTITUTION_SYMBOLS;
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}
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return replace.call(replacement, symbols, function (match, ch) {
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var capture;
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switch (ch.charAt(0)) {
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case '$': return '$';
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case '&': return matched;
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case '`': return str.slice(0, position);
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case "'": return str.slice(tailPos);
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case '<':
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capture = namedCaptures[ch.slice(1, -1)];
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break;
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default: // \d\d?
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var n = +ch;
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if (n === 0) return match;
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if (n > m) {
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var f = floor(n / 10);
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if (f === 0) return match;
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if (f <= m) return captures[f - 1] === undefined ? ch.charAt(1) : captures[f - 1] + ch.charAt(1);
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return match;
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}
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capture = captures[n - 1];
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}
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return capture === undefined ? '' : capture;
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});
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};
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