'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 aString = require('../internals/a-string');
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var hasOwn = require('../internals/has-own-property');
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var padStart = require('../internals/string-pad').start;
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var WHITESPACES = require('../internals/whitespaces');
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var $Array = Array;
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var $escape = RegExp.escape;
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var charAt = uncurryThis(''.charAt);
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var charCodeAt = uncurryThis(''.charCodeAt);
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var numberToString = uncurryThis(1.1.toString);
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var join = uncurryThis([].join);
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var FIRST_DIGIT_OR_ASCII = /^[0-9a-z]/i;
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var SYNTAX_SOLIDUS = /^[$()*+./?[\\\]^{|}]/;
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var OTHER_PUNCTUATORS_AND_WHITESPACES = RegExp('^[!"#%&\',\\-:;<=>@`~' + WHITESPACES + ']');
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var exec = uncurryThis(FIRST_DIGIT_OR_ASCII.exec);
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var ControlEscape = {
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'\u0009': 't',
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'\u000A': 'n',
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'\u000B': 'v',
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'\u000C': 'f',
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'\u000D': 'r'
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};
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var escapeChar = function (chr) {
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var hex = numberToString(charCodeAt(chr, 0), 16);
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return hex.length < 3 ? '\\x' + padStart(hex, 2, '0') : '\\u' + padStart(hex, 4, '0');
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};
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// Avoiding the use of polyfills of the previous iteration of this proposal
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var FORCED = !$escape || $escape('ab') !== '\\x61b';
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// `RegExp.escape` method
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// https://tc39.es/ecma262/#sec-regexp.escape
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$({ target: 'RegExp', stat: true, forced: FORCED }, {
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escape: function escape(S) {
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aString(S);
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var length = S.length;
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var result = $Array(length);
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for (var i = 0; i < length; i++) {
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var chr = charAt(S, i);
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if (i === 0 && exec(FIRST_DIGIT_OR_ASCII, chr)) {
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result[i] = escapeChar(chr);
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} else if (hasOwn(ControlEscape, chr)) {
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result[i] = '\\' + ControlEscape[chr];
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} else if (exec(SYNTAX_SOLIDUS, chr)) {
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result[i] = '\\' + chr;
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} else if (exec(OTHER_PUNCTUATORS_AND_WHITESPACES, chr)) {
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result[i] = escapeChar(chr);
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} else {
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var charCode = charCodeAt(chr, 0);
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// single UTF-16 code unit
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if ((charCode & 0xF800) !== 0xD800) result[i] = chr;
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// unpaired surrogate
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else if (charCode >= 0xDC00 || i + 1 >= length || (charCodeAt(S, i + 1) & 0xFC00) !== 0xDC00) result[i] = escapeChar(chr);
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// surrogate pair
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else {
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result[i] = chr;
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result[++i] = charAt(S, i);
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}
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}
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}
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return join(result, '');
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}
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});
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