47 lines
1.3 KiB
JavaScript
47 lines
1.3 KiB
JavaScript
'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;
|
|
};
|