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add Array.prototype.flatMap and Array.prototype.flat #1309

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ljharb merged 1 commit into from
Feb 26, 2019
Merged

add Array.prototype.flatMap and Array.prototype.flat #1309

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61 changes: 60 additions & 1 deletion spec.html
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Original file line number Diff line number Diff line change
Expand Up @@ -31806,6 +31806,63 @@ <h1>Array.prototype.findIndex ( _predicate_ [ , _thisArg_ ] )</h1>
</emu-note>
</emu-clause>

<emu-clause id="sec-array.prototype.flat">
<h1>Array.prototype.flat( [ _depth_ ] )</h1>
<p>When the `flat` method is called with zero or one arguments, the following steps are taken:</p>
<emu-alg>
1. Let _O_ be ? ToObject(*this* value).
1. Let _sourceLen_ be ? ToLength(? Get(_O_, `"length"`)).
1. Let _depthNum_ be 1.
1. If _depth_ is not *undefined*, then
1. Set _depthNum_ to ? ToInteger(_depth_).
1. Let _A_ be ? ArraySpeciesCreate(_O_, 0).
1. Perform ? FlattenIntoArray(_A_, _O_, _sourceLen_, 0, _depthNum_).
1. Return _A_.
</emu-alg>

<emu-clause id="sec-flattenintoarray" aoid="FlattenIntoArray">
<h1>FlattenIntoArray(_target_, _source_, _sourceLen_, _start_, _depth_ [ , _mapperFunction_, _thisArg_ ])</h1>
<emu-alg>
1. Let _targetIndex_ be _start_.
1. Let _sourceIndex_ be 0.
1. Repeat, while _sourceIndex_ &lt; _sourceLen_
1. Let _P_ be ! ToString(_sourceIndex_).
1. Let _exists_ be ? HasProperty(_source_, _P_).
1. If _exists_ is *true*, then
1. Let _element_ be ? Get(_source_, _P_).
1. If _mapperFunction_ is present, then
1. Assert: _thisArg_ is present.
1. Set _element_ to ? Call(_mapperFunction_, _thisArg_ , &laquo; _element_, _sourceIndex_, _source_ &raquo;).
1. Let _shouldFlatten_ be *false*.
1. If _depth_ &gt; 0, then
1. Set _shouldFlatten_ to ? IsArray(_element_).
1. If _shouldFlatten_ is *true*, then
1. Let _elementLen_ be ? ToLength(? Get(_element_, `"length"`)).
1. Set _targetIndex_ to ? FlattenIntoArray(_target_, _element_, _elementLen_, _targetIndex_, _depth_ - 1).
1. Else,
1. If _targetIndex_ &ge; 2<sup>53</sup>-1, throw a *TypeError* exception.
1. Perform ? CreateDataPropertyOrThrow(_target_, ! ToString(_targetIndex_), _element_).
1. Increase _targetIndex_ by 1.
1. Increase _sourceIndex_ by 1.
1. Return _targetIndex_.
</emu-alg>
</emu-clause>
</emu-clause>

<emu-clause id="sec-array.prototype.flatmap">
<h1>Array.prototype.flatMap ( _mapperFunction_ [ , _thisArg_ ] )</h1>
<p>When the `flatMap` method is called with one or two arguments, the following steps are taken:</p>
<emu-alg>
1. Let _O_ be ? ToObject(*this* value).
1. Let _sourceLen_ be ? ToLength(? Get(_O_, `"length"`)).
1. If IsCallable(_mapperFunction_) is *false*, throw a *TypeError* exception.
1. If _thisArg_ is present, let _T_ be _thisArg_; else let _T_ be *undefined*.
1. Let _A_ be ? ArraySpeciesCreate(_O_, 0).
1. Perform ? FlattenIntoArray(_A_, _O_, _sourceLen_, 0, 1, _mapperFunction_, _T_).
1. Return _A_.
</emu-alg>
</emu-clause>

<emu-clause id="sec-array.prototype.foreach">
<h1>Array.prototype.forEach ( _callbackfn_ [ , _thisArg_ ] )</h1>
<emu-note>
Expand Down Expand Up @@ -32596,10 +32653,12 @@ <h1>Array.prototype [ @@unscopables ]</h1>
1. Perform CreateDataProperty(_unscopableList_, `"fill"`, *true*).
1. Perform CreateDataProperty(_unscopableList_, `"find"`, *true*).
1. Perform CreateDataProperty(_unscopableList_, `"findIndex"`, *true*).
1. Perform CreateDataProperty(_unscopableList_, `"flat"`, *true*).
1. Perform CreateDataProperty(_unscopableList_, `"flatMap"`, *true*).
1. Perform CreateDataProperty(_unscopableList_, `"includes"`, *true*).
1. Perform CreateDataProperty(_unscopableList_, `"keys"`, *true*).
1. Perform CreateDataProperty(_unscopableList_, `"values"`, *true*).
1. Assert: Each of the above calls will return *true*.
1. Assert: Each of the above calls returns *true*.
1. Return _unscopableList_.
</emu-alg>
<p>This property has the attributes { [[Writable]]: *false*, [[Enumerable]]: *false*, [[Configurable]]: *true* }.</p>
Expand Down