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Normative: Add getOrInsert and getOrInsertComputed methods for Map and WeakMap #3740

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Merged
ljharb merged 1 commit into from
Jan 22, 2026
Merged

Normative: Add getOrInsert and getOrInsertComputed methods for Map and WeakMap #3740

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74 changes: 74 additions & 0 deletions spec.html
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Original file line number Diff line number Diff line change
Expand Up @@ -43650,6 +43650,43 @@ <h1>Map.prototype.get ( _key_ )</h1>
</emu-alg>
</emu-clause>

<emu-clause id="sec-map.prototype.getorinsert">
<h1>Map.prototype.getOrInsert ( _key_, _value_ )</h1>
<p>This method performs the following steps when called:</p>
<emu-alg>
1. Let _M_ be the *this* value.
1. Perform ? RequireInternalSlot(_M_, [[MapData]]).
1. Set _key_ to CanonicalizeKeyedCollectionKey(_key_).
1. For each Record { [[Key]], [[Value]] } _p_ of _M_.[[MapData]], do
1. If _p_.[[Key]] is not ~empty~ and SameValue(_p_.[[Key]], _key_) is *true*, return _p_.[[Value]].
1. Let _p_ be the Record { [[Key]]: _key_, [[Value]]: _value_ }.
1. Append _p_ to _M_.[[MapData]].
1. Return _value_.
</emu-alg>
</emu-clause>

<emu-clause id="sec-map.prototype.getorinsertcomputed">
<h1>Map.prototype.getOrInsertComputed ( _key_, _callback_ )</h1>
<p>This method performs the following steps when called:</p>
<emu-alg>
1. Let _M_ be the *this* value.
1. Perform ? RequireInternalSlot(_M_, [[MapData]]).
1. If IsCallable(_callback_) is *false*, throw a *TypeError* exception.
1. Set _key_ to CanonicalizeKeyedCollectionKey(_key_).
1. For each Record { [[Key]], [[Value]] } _p_ of _M_.[[MapData]], do
1. If _p_.[[Key]] is not ~empty~ and SameValue(_p_.[[Key]], _key_) is *true*, return _p_.[[Value]].
1. Let _value_ be ? Call(_callback_, *undefined*, « _key_ »).
1. NOTE: The Map may have been modified during execution of _callback_.
1. For each Record { [[Key]], [[Value]] } _p_ of _M_.[[MapData]], do
1. If _p_.[[Key]] is not ~empty~ and SameValue(_p_.[[Key]], _key_) is *true*, then
1. Set _p_.[[Value]] to _value_.
1. Return _value_.
1. Let _p_ be the Record { [[Key]]: _key_, [[Value]]: _value_ }.
1. Append _p_ to _M_.[[MapData]].
1. Return _value_.
</emu-alg>
</emu-clause>

<emu-clause id="sec-map.prototype.has">
<h1>Map.prototype.has ( _key_ )</h1>
<p>This method performs the following steps when called:</p>
Expand Down Expand Up @@ -44526,6 +44563,43 @@ <h1>WeakMap.prototype.get ( _key_ )</h1>
</emu-alg>
</emu-clause>

<emu-clause id="sec-weakmap.prototype.getorinsert">
<h1>WeakMap.prototype.getOrInsert ( _key_, _value_ )</h1>
<p>This method performs the following steps when called:</p>
<emu-alg>
1. Let _M_ be the *this* value.
1. Perform ? RequireInternalSlot(_M_, [[WeakMapData]]).
1. If CanBeHeldWeakly(_key_) is *false*, throw a *TypeError* exception.
1. For each Record { [[Key]], [[Value]] } _p_ of _M_.[[WeakMapData]], do
1. If _p_.[[Key]] is not ~empty~ and SameValue(_p_.[[Key]], _key_) is *true*, return _p_.[[Value]].
1. Let _p_ be the Record { [[Key]]: _key_, [[Value]]: _value_ }.
1. Append _p_ to _M_.[[WeakMapData]].
1. Return _value_.
</emu-alg>
</emu-clause>

<emu-clause id="sec-weakmap.prototype.getorinsertcomputed">
<h1>WeakMap.prototype.getOrInsertComputed ( _key_, _callback_ )</h1>
<p>This method performs the following steps when called:</p>
<emu-alg>
1. Let _M_ be the *this* value.
1. Perform ? RequireInternalSlot(_M_, [[WeakMapData]]).
1. If CanBeHeldWeakly(_key_) is *false*, throw a *TypeError* exception.
1. If IsCallable(_callback_) is *false*, throw a *TypeError* exception.
1. For each Record { [[Key]], [[Value]] } _p_ of _M_.[[WeakMapData]], do
1. If _p_.[[Key]] is not ~empty~ and SameValue(_p_.[[Key]], _key_) is *true*, return _p_.[[Value]].
1. Let _value_ be ? Call(_callback_, *undefined*, « _key_ »).
1. NOTE: The WeakMap may have been modified during execution of _callback_.
1. For each Record { [[Key]], [[Value]] } _p_ of _M_.[[WeakMapData]], do
1. If _p_.[[Key]] is not ~empty~ and SameValue(_p_.[[Key]], _key_) is *true*, then
1. Set _p_.[[Value]] to _value_.
1. Return _value_.
1. Let _p_ be the Record { [[Key]]: _key_, [[Value]]: _value_ }.
1. Append _p_ to _M_.[[WeakMapData]].
1. Return _value_.
</emu-alg>
</emu-clause>

<emu-clause id="sec-weakmap.prototype.has">
<h1>WeakMap.prototype.has ( _key_ )</h1>
<p>This method performs the following steps when called:</p>
Expand Down
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