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node_modules/es-abstract/2015/AdvanceStringIndex.js

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