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Programming-Idioms

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Idiom #51 Check if map contains key

Determine whether the map m contains an entry for the key k

_m.has(_k)

Uses an actual Map instance, rather than relying on objects and their keys
k in m

This will lookup a property in the object and its entire prototype chain.
m.hasOwnProperty(k)

This is like "k in m" except it doesn't check up the prototype chain, which is often not what people want.
M.Contains (K)
New implementation...
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programming-idioms.org 
_m.has(_k)
k in m
m.hasOwnProperty(k)
M.Contains (K)
(contains? m k)
bool key_exists = m.find(k) != m.end();
bool key_exists = m.contains(k);
bool key_exists = m.count(k) != 0;
bool keyExists = m.ContainsKey(key)
if (k in m) { }
m.containsKey(k)
Map.has_key?(m, k)
maps:is_key(K, M).
_, ok := m[k]
Map.member k m
(/=Nothing) (lookup k m)

m.containsKey(k)
m.containsKey(k)
(nth-value 1 (gethash k m))
m[k] ~= nil
if (m[k]) ...
array_key_exists($k, $m)
m.IndexOf(k) >= 0
exists $m->{$k}
m.get(k)
k in m
m.key?(k)
m.has_key?(k)
m.include?(k)

m.contains_key(&k)
m.contains(k)
(assoc k m)
m includesKey: k.
If m.ContainsKey(k) Then...