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<pre class="metadata">
title: String.prototype.codePoints
stage: 1
contributors: Ingvar Stepanyan
</pre>
<!-- es6num="21.1.3" -->
<emu-clause id="sec-properties-of-the-string-prototype-object">
<h1>Properties of the String Prototype Object</h1>
<!-- es6num="21.1.3.27" -->
<emu-clause id="sec-string.prototype-@@iterator">
<h1>String.prototype [ @@iterator ] ( )</h1>
<p>When the @@iterator method is called it returns an Iterator object (<emu-xref href="#sec-iterator-interface"></emu-xref>) that iterates over the code points of a String value, returning each code point as a String value. The following steps are taken:</p>
<emu-alg>
1. Let _O_ be ? RequireObjectCoercible(*this* value).
1. Let _S_ be ? ToString(_O_).
1. Return CreateStringIterator(_S_, <ins>`"string"`</ins>).
</emu-alg>
<p>The value of the `name` property of this function is `"[Symbol.iterator]"`.</p>
</emu-clause>
<ins class="block">
<!-- es6num="21.1.3.28" -->
<emu-clause id="sec-string.prototype-codepoints">
<h1>String.prototype.codePoints ( )</h1>
<p>When the `codePoints` method is called it returns an Iterator object (<emu-xref href="#sec-iterator-interface"></emu-xref>) that iterates over the code points of a String value, returning a descriptor consisting of position within a string and code point itself as a Number value. The following steps are taken:</p>
<emu-alg>
1. Let _O_ be ? RequireObjectCoercible(*this* value).
1. Let _S_ be ? ToString(_O_).
1. Return CreateStringIterator(_S_, <ins>`"descriptor"`</ins>).
</emu-alg>
</emu-clause>
</ins>
</emu-clause>
<!-- es6num="21.1.5" -->
<emu-clause id="sec-string-iterator-objects">
<h1>String Iterator Objects</h1>
<!-- es6num="21.1.5.1" -->
<emu-clause id="sec-createstringiterator" aoid="CreateStringIterator">
<h1>CreateStringIterator ( _string_, <ins>_kind_</ins> )</h1>
<p>Several methods of String objects return Iterator objects. The abstract operation CreateStringIterator with argument _string_ is used to create such iterator objects. It performs the following steps:</p>
<emu-alg>
1. Assert: Type(_string_) is String.
1. Let _iterator_ be ObjectCreate(%StringIteratorPrototype%, « [[IteratedString]], [[StringIteratorNextIndex]] »).
1. Set _iterator_.[[IteratedString]] to _string_.
1. Set _iterator_.[[StringIteratorNextIndex]] to 0.
1. <ins>Set _iterator_.[[StringIterationKind]] to _kind_.</ins>
1. Return _iterator_.
</emu-alg>
</emu-clause>
<!-- es6num="21.1.5.2" -->
<emu-clause id="sec-%stringiteratorprototype%-object">
<h1>The %StringIteratorPrototype% Object</h1>
<!-- es6num="21.1.5.2.1" -->
<emu-clause id="sec-%stringiteratorprototype%.next">
<h1>%StringIteratorPrototype%.next ( )</h1>
<emu-alg>
1. Let _O_ be the *this* value.
1. If Type(_O_) is not Object, throw a *TypeError* exception.
1. If _O_ does not have all of the internal slots of a String Iterator Instance (<emu-xref href="#sec-properties-of-string-iterator-instances"></emu-xref>), throw a *TypeError* exception.
1. Let _s_ be _O_.[[IteratedString]].
1. If _s_ is *undefined*, return CreateIterResultObject(*undefined*, *true*).
1. Let _position_ be _O_.[[StringIteratorNextIndex]].
1. Let _len_ be the length of _s_.
1. If _position_ <del>≥</del> <ins>==</ins> _len_, then
1. Set _O_.[[IteratedString]] to *undefined*.
1. <ins>If _itemKind_ is `"string"`, let _result_ be *undefined*.</ins>
1. <ins>Else,</ins>
1. <ins>Assert: _itemKind_ is `"descriptor"`.</ins>
1. <ins>Let _result_ be ObjectCreate(%ObjectPrototype%).</ins>
1. <ins>Perform CreateDataProperty(_result_, `"position"`, _len_).</ins>
1. <ins>Perform CreateDataProperty(_result_, `"codePoint"`, *undefined*).</ins>
1. <del>Return CreateIterResultObject(*undefined*, *true*)</del>.
1. <ins>Return CreateIterResultObject(_result_, *true*)</ins>.
1. <ins>Let _itemKind_ be _O_.[[StringIterationKind]].</ins>
1. Let _first_ be the numeric value of the code unit at index _position_ within _s_.
1. <del>If _first_ < 0xD800 or _first_ > 0xDBFF or _position_+1 = _len_, let _resultString_ be the String value consisting of the single code unit _first_.</del>
1. <ins>If _first_ ≥ 0xD800 and _first_ ≤ 0xDBFF and _position_+1 < _len_, then
1. Let _second_ be the numeric value of the code unit at index _position_+1 within the String _S_.
1. <del>If _second_ < 0xDC00 or _second_ > 0xDFFF, let _resultString_ be the String value consisting of the single code unit _first_.</del>
1. <del>Else, let _resultString_ be the string-concatenation of the code unit _first_ and the code unit _second_.</del>
1. <ins>If _second_ ≥ 0xDC00 and _second_ ≤ 0xDFFF, then</ins>
1. <ins>Set _O_.[[StringIteratorNextIndex]] to _position_ + 2.</ins>
1. <ins>If _itemKind_ is `"string"`, let _result_ be the string-concatenation of the code unit _first_ and the code unit _second_.
1. <ins>Else,</ins>
1. <ins>Assert: _itemKind_ is `"descriptor"`.</ins>
1. <ins>Let _resultCp_ be UTF16Decode(_first_, _second_).</ins>
1. <ins>Let _result_ be ObjectCreate(%ObjectPrototype%).</ins>
1. <ins>Perform CreateDataProperty(_result_, `"position"`, _position_).</ins>
1. <ins>Perform CreateDataProperty(_result_, `"codePoint"`, _resultCp_).</ins>
1. <ins>Return CreateIterResultObject(_result_, *false*).</ins>
1. <del>Let _resultSize_ be the number of code units in _resultString_.</del>
1. <del>Set _O_.[[StringIteratorNextIndex]] to _position_ + _resultSize_.</del>
1. <ins>Set _O_.[[StringIteratorNextIndex]] to _position_ + 1.</ins>
1. <ins>If _itemKind_ is `"string"`, let _result_ be the String value consisting of the single code unit _first_.
1. <ins>Else,</ins>
1. <ins>Assert: _itemKind_ is `"descriptor"`.</ins>
1. <ins>Let _result_ be ObjectCreate(%ObjectPrototype%).</ins>
1. <ins>Perform CreateDataProperty(_result_, `"position"`, _position_).</ins>
1. <ins>Perform CreateDataProperty(_result_, `"codePoint"`, _first_).</ins>
1. <ins>Return CreateIterResultObject(<del>_resultString_</del><ins>_result_</ins>, *false*).</ins>
</emu-alg>
</emu-clause>
</emu-clause>
<!-- es6num="21.1.5.3" -->
<emu-clause id="sec-properties-of-string-iterator-instances">
<h1>Properties of String Iterator Instances</h1>
<p>String Iterator instances are ordinary objects that inherit properties from the %StringIteratorPrototype% intrinsic object. String Iterator instances are initially created with the internal slots listed in <emu-xref href="#table-46"></emu-xref>.</p>
<emu-table id="table-46" caption="Internal Slots of String Iterator Instances">
<table>
<tbody>
<tr>
<th>
Internal Slot
</th>
<th>
Description
</th>
</tr>
<tr>
<td>
[[IteratedString]]
</td>
<td>
The String value whose elements are being iterated.
</td>
</tr>
<tr>
<td>
[[StringIteratorNextIndex]]
</td>
<td>
The integer index of the next string index to be examined by this iteration.
</td>
</tr>
<tr>
<td>
<ins>[[StringIterationKind]]</ins>
</td>
<td>
<ins>A String value that identifies what is to be returned for each element of the iteration. The possible values are: `"string"`, `"descriptor"`.</ins>
</td>
</tr>
</tbody>
</table>
</emu-table>
</emu-clause>
</emu-clause>