| '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; |
| }; |