2 files changed, 483 insertions, 288 deletions

diff --git a/src/gleam/map.gleam b/src/gleam/map.gleam
index 7fd363f..ebb199a 100644
--- a/src/gleam/map.gleam
+++ b/src/gleam/map.gleam
@@ -1,329 +1,460 @@
+import gleam/result
+import gleam/option.{Option}
+import gleam/list
+
+/// A dictionary of keys and values.
+///
+/// Any type can be used for the keys and values of a map, but all the keys
+/// must be of the same type and all the values must be of the same type.
+///
+/// Each key can only be present in a map once.
+///
+/// Maps are not ordered in any way, and any unintentional ordering is not to
+/// be relied upon in your code as it may change in future versions of Erlang
+/// or Gleam.
+///
+/// See [the Erlang map module](https://erlang.org/doc/man/maps.html) for more
+/// information.
+///
+pub external type Map(key, value)
+
+/// Determines the number of key-value pairs in the map.
+/// This function runs in constant time and does not need to iterate the map.
+///
+/// ## Examples
+///
+///    > new() |> size()
+///    0
+///
+///    > new() |> insert("key", "value") |> size()
+///    1
+///
+///
+pub fn size(map: Map(k, v)) -> Int {
+  do_size(map)
+}
+
 if erlang {
-  import gleam/result
-  import gleam/option.{Option}
-  import gleam/list
-
-  /// A dictionary of keys and values.
-  ///
-  /// Any type can be used for the keys and values of a map, but all the keys
-  /// must be of the same type and all the values must be of the same type.
-  ///
-  /// Each key can only be present in a map once.
-  ///
-  /// Maps are not ordered in any way, and any unintentional ordering is not to
-  /// be relied upon in your code as it may change in future versions of Erlang
-  /// or Gleam.
-  ///
-  /// See [the Erlang map module](https://erlang.org/doc/man/maps.html) for more
-  /// information.
-  ///
-  pub external type Map(key, value)
-
-  /// Determines the number of key-value pairs in the map.
-  /// This function runs in constant time and does not need to iterate the map.
-  ///
-  /// ## Examples
-  ///
-  ///    > new() |> size()
-  ///    0
-  ///
-  ///    > new() |> insert("key", "value") |> size()
-  ///    1
-  ///
-  ///
-  pub external fn size(Map(k, v)) -> Int =
+  external fn do_size(Map(k, v)) -> Int =
     "maps" "size"
+}
+
+if javascript {
+  external fn do_size(Map(k, v)) -> Int =
+    "../gleam_stdlib.js" "map_size"
+}
+
+/// Converts the map to a list of 2-element tuples `#(key, value)`, one for
+/// each key-value pair in the map.
+///
+/// The tuples in the list have no specific order.
+///
+/// ## Examples
+///
+///    > new() |> to_list()
+///    []
+///
+///    > new() |> insert("key", 0) |> to_list()
+///    [#("key", 0)]
+///
+pub fn to_list(map: Map(key, value)) -> List(#(key, value)) {
+  do_to_list(map)
+}
 
-  /// Converts the map to a list of 2-element tuples `#(key, value)`, one for
-  /// each key-value pair in the map.
-  ///
-  /// The tuples in the list have no specific order.
-  ///
-  /// ## Examples
-  ///
-  ///    > new() |> to_list()
-  ///    []
-  ///
-  ///    > new() |> insert("key", 0) |> to_list()
-  ///    [#("key", 0)]
-  ///
-  pub external fn to_list(Map(key, value)) -> List(#(key, value)) =
+if erlang {
+  external fn do_to_list(Map(key, value)) -> List(#(key, value)) =
     "maps" "to_list"
+}
+
+if javascript {
+  external fn do_to_list(Map(key, value)) -> List(#(key, value)) =
+    "../gleam_stdlib.js" "map_to_list"
+}
+
+/// Converts a list of 2-element tuples `#(key, value)` to a map.
+///
+/// If two tuples have the same key the last one in the list will be the one
+/// that is present in the map.
+///
+pub fn from_list(list: List(#(key, value))) -> Map(key, value) {
+  do_from_list(list)
+}
 
-  /// Converts a list of 2-element tuples `#(key, value)` to a map.
-  ///
-  /// If two tuples have the same key the last one in the list will be the one
-  /// that is present in the map.
-  ///
-  pub external fn from_list(List(#(key, value))) -> Map(key, value) =
+if erlang {
+  external fn do_from_list(List(#(key, value))) -> Map(key, value) =
     "maps" "from_list"
+}
+
+if javascript {
+  external fn do_from_list(List(#(key, value))) -> Map(key, value) =
+    "../gleam_stdlib.js" "map_to_list"
+}
+
+/// Determines whether or not a value present in the map for a given key.
+///
+/// ## Examples
+///
+///    > new() |> insert("a", 0) |> has_key("a")
+///    True
+///
+///    > new() |> insert("a", 0) |> has_key("b")
+///    False
+///
+pub fn has_key(map: Map(k, v), key: k) -> Bool {
+  do_has_key(key, map)
+}
 
-  external fn is_key(key, Map(key, v)) -> Bool =
+if erlang {
+  external fn do_has_key(key, Map(key, v)) -> Bool =
     "maps" "is_key"
+}
 
-  /// Determines whether or not a value present in the map for a given key.
-  ///
-  /// ## Examples
-  ///
-  ///    > new() |> insert("a", 0) |> has_key("a")
-  ///    True
-  ///
-  ///    > new() |> insert("a", 0) |> has_key("b")
-  ///    False
-  ///
-  pub fn has_key(map: Map(k, v), key: k) -> Bool {
-    is_key(key, map)
-  }
+if javascript {
+  external fn do_has_key(k, Map(k, v)) -> Bool =
+    "../gleam_stdlib.js" "map_has_key"
+}
+
+/// Creates a fresh map that contains no values.
+///
+pub fn new() -> Map(key, value) {
+  do_new()
+}
 
-  /// Creates a fresh map that contains no values.
-  ///
-  pub external fn new() -> Map(key, value) =
+if erlang {
+  external fn do_new() -> Map(key, value) =
     "maps" "new"
+}
+
+if javascript {
+  external fn do_new() -> Map(key, value) =
+    "../gleam_stdlib.js" "new_map"
+}
+
+/// Fetches a value from a map for a given key.
+///
+/// The map may not have a value for the key, so the value is wrapped in a
+/// Result.
+///
+/// ## Examples
+///
+///    > new() |> insert("a", 0) |> get("a")
+///    Ok(0)
+///
+///    > new() |> insert("a", 0) |> get("b")
+///    Error(Nil)
+///
+pub fn get(from: Map(key, value), get: key) -> Result(value, Nil) {
+  do_get(from, get);
+}
 
-  /// Fetches a value from a map for a given key.
-  ///
-  /// The map may not have a value for the key, so the value is wrapped in a
-  /// Result.
-  ///
-  /// ## Examples
-  ///
-  ///    > new() |> insert("a", 0) |> get("a")
-  ///    Ok(0)
-  ///
-  ///    > new() |> insert("a", 0) |> get("b")
-  ///    Error(Nil)
-  ///
-  pub external fn get(from: Map(key, value), get: key) -> Result(value, Nil) =
+if erlang {
+  external fn do_get(Map(key, value), key) -> Result(value, Nil) =
     "gleam_stdlib" "map_get"
+}
+
+if javascript {
+  external fn do_get(Map(key, value), key) -> Result(value, Nil) =
+    "../gleam_stdlib.js" "map_get"
+}
+
+/// Inserts a value into the map with the given key.
+///
+/// If the map already has a value for the given key then the value is
+/// replaced with the new value.
+///
+/// ## Examples
+///
+///    > new() |> insert("a", 0) |> to_list
+///    [#("a", 0)]
+///
+///    > new() |> insert("a", 0) |> insert("a", 5) |> to_list
+///    [#("a", 5)]
+///
+pub fn insert(into map: Map(k, v), for key: k, insert value: v) -> Map(k, v) {
+  do_insert(key, value, map)
+}
 
-  external fn erl_insert(key, value, Map(key, value)) -> Map(key, value) =
+if erlang {
+  external fn do_insert(key, value, Map(key, value)) -> Map(key, value) =
     "maps" "put"
+}
 
-  /// Inserts a value into the map with the given key.
-  ///
-  /// If the map already has a value for the given key then the value is
-  /// replaced with the new value.
-  ///
-  /// ## Examples
-  ///
-  ///    > new() |> insert("a", 0) |> to_list
-  ///    [#("a", 0)]
-  ///
-  ///    > new() |> insert("a", 0) |> insert("a", 5) |> to_list
-  ///    [#("a", 5)]
-  ///
-  pub fn insert(into map: Map(k, v), for key: k, insert value: v) -> Map(k, v) {
-    erl_insert(key, value, map)
-  }
+if javascript {
+  external fn do_insert(key, value, Map(key, value)) -> Map(key, value) =
+    "../gleam_stdlib.js" "map_insert"
+}
+
+/// Updates all values in a given map by calling a given function on each key
+/// and value.
+///
+/// ## Examples
+///
+///    > [#(3, 3), #(2, 4)]
+///    > |> from_list
+///    > |> map_values(fn(key, value) { key * value })
+///    [#(3, 9), #(2, 8)]
+///
+///
+pub fn map_values(in map: Map(k, v), with fun: fn(k, v) -> w) -> Map(k, w) {
+  do_map_values(fun, map)
+}
 
-  external fn erl_map_values(fn(key, a) -> b, Map(key, value)) -> Map(key, b) =
+if erlang {
+  external fn do_map_values(fn(key, a) -> b, Map(key, value)) -> Map(key, b) =
     "maps" "map"
+}
 
-  /// Updates all values in a given map by calling a given function on each key
-  /// and value.
-  ///
-  /// ## Examples
-  ///
-  ///    > [#(3, 3), #(2, 4)]
-  ///    > |> from_list
-  ///    > |> map_values(fn(key, value) { key * value })
-  ///    [#(3, 9), #(2, 8)]
-  ///
-  ///
-  pub fn map_values(in map: Map(k, v), with fun: fn(k, v) -> w) -> Map(k, w) {
-    erl_map_values(fun, map)
-  }
+if javascript {
+  external fn do_map_values(fn(key, a) -> b, Map(key, value)) -> Map(key, b) =
+    "../gleam_stdlib.js" "map_map_values"
+}
+
+/// Gets a list of all keys in a given map.
+///
+/// Maps are not ordered so the keys are not returned in any specific order. Do
+/// not write code that relies on the order keys are returned by this function
+/// as it may change in later versions of Gleam or Erlang.
+///
+/// ## Examples
+///
+///    > keys([#("a", 0), #("b", 1)])
+///    ["a", "b"]
+///
+pub fn keys(map: Map(keys, v)) -> List(keys) {
+  do_keys(map)
+}
 
-  /// Gets a list of all keys in a given map.
-  ///
-  /// Maps are not ordered so the keys are not returned in any specific order. Do
-  /// not write code that relies on the order keys are returned by this function
-  /// as it may change in later versions of Gleam or Erlang.
-  ///
-  /// ## Examples
-  ///
-  ///    > keys([#("a", 0), #("b", 1)])
-  ///    ["a", "b"]
-  ///
-  pub external fn keys(Map(keys, v)) -> List(keys) =
+if erlang {
+  external fn do_keys(Map(keys, v)) -> List(keys) =
     "maps" "keys"
+}
+
+if javascript {
+  external fn do_keys(Map(keys, v)) -> List(keys) =
+    "../gleam_stdlib.js" "map_keys"
+}
+
+/// Gets a list of all values in a given map.
+///
+/// Maps are not ordered so the values are not returned in any specific order. Do
+/// not write code that relies on the order values are returned by this function
+/// as it may change in later versions of Gleam or Erlang.
+///
+/// ## Examples
+///
+///    > keys(from_list([#("a", 0), #("b", 1)]))
+///    [0, 1]
+///
+pub fn values(map: Map(k, values)) -> List(values) {
+  do_values(map)
+}
 
-  /// Gets a list of all values in a given map.
-  ///
-  /// Maps are not ordered so the values are not returned in any specific order. Do
-  /// not write code that relies on the order values are returned by this function
-  /// as it may change in later versions of Gleam or Erlang.
-  ///
-  /// ## Examples
-  ///
-  ///    > keys(from_list([#("a", 0), #("b", 1)]))
-  ///    [0, 1]
-  ///
-  pub external fn values(Map(k, values)) -> List(values) =
+if erlang {
+  external fn do_values(Map(k, values)) -> List(values) =
     "maps" "values"
+}
+
+if javascript {
+  external fn do_values(Map(k, values)) -> List(values) =
+    "../gleam_stdlib.js" "map_values"
+}
+
+/// Creates a new map from a given map, minus any entries that a given function
+/// returns False for.
+///
+/// ## Examples
+///
+///    > from_list([#("a", 0), #("b", 1)])
+///    > |> filter(fn(key, value) { value != 0 })
+///    from_list([#("b", 1)])
+///
+///    > from_list([#("a", 0), #("b", 1)])
+///    > |> filter(fn(key, value) { True })
+///    from_list([#("a", 0), #("b", 1)])
+///
+pub fn filter(in map: Map(k, v), for property: fn(k, v) -> Bool) -> Map(k, v) {
+  do_filter(property, map)
+}
 
-  external fn erl_filter(
+if erlang {
+  external fn do_filter(
     fn(key, value) -> Bool,
     Map(key, value),
   ) -> Map(key, value) =
     "maps" "filter"
+}
 
-  /// Creates a new map from a given map, minus any entries that a given function
-  /// returns False for.
-  ///
-  /// ## Examples
-  ///
-  ///    > from_list([#("a", 0), #("b", 1)])
-  ///    > |> filter(fn(key, value) { value != 0 })
-  ///    from_list([#("b", 1)])
-  ///
-  ///    > from_list([#("a", 0), #("b", 1)])
-  ///    > |> filter(fn(key, value) { True })
-  ///    from_list([#("a", 0), #("b", 1)])
-  ///
-  pub fn filter(in map: Map(k, v), for property: fn(k, v) -> Bool) -> Map(k, v) {
-    erl_filter(property, map)
-  }
+if javascript {
+  external fn do_filter(
+    fn(key, value) -> Bool,
+    Map(key, value),
+  ) -> Map(key, value) =
+    "../gleam_stdlib.js" "map_filter"
+}
 
-  external fn erl_take(List(k), Map(k, v)) -> Map(k, v) =
-    "maps" "with"
-
-  /// Creates a new map from a given map, only including any entries for which the
-  /// keys are in a given list.
-  ///
-  /// ## Examples
-  ///
-  ///    > from_list([#("a", 0), #("b", 1)])
-  ///    > |> take(["b"])
-  ///    from_list([#("b", 1)])
-  ///
-  ///    > from_list([#("a", 0), #("b", 1)])
-  ///    > |> take(["a", "b", "c"])
-  ///    from_list([#("a", 0), #("b", 1)])
-  ///
-  pub fn take(from map: Map(k, v), keeping desired_keys: List(k)) -> Map(k, v) {
-    erl_take(desired_keys, map)
-  }
+/// Creates a new map from a given map, only including any entries for which the
+/// keys are in a given list.
+///
+/// ## Examples
+///
+///    > from_list([#("a", 0), #("b", 1)])
+///    > |> take(["b"])
+///    from_list([#("b", 1)])
+///
+///    > from_list([#("a", 0), #("b", 1)])
+///    > |> take(["a", "b", "c"])
+///    from_list([#("a", 0), #("b", 1)])
+///
+pub fn take(from map: Map(k, v), keeping desired_keys: List(k)) -> Map(k, v) {
+  do_take(desired_keys, map)
+}
 
-  /// Creates a new map from a pair of given maps by combining their entries.
-  ///
-  /// If there are entries with the same keys in both maps the entry from the
-  /// second map takes precedence.
-  ///
-  /// ## Examples
-  ///
-  ///    > let a = from_list([#("a", 0), #("b", 1)])
-  ///    > let b = from_list([#("b", 2), #("c", 3)])
-  ///    > merge(a, b)
-  ///    from_list([#("a", 0), #("b", 2), #("c", 3)])
-  ///
-  pub external fn merge(into: Map(k, v), merge: Map(k, v)) -> Map(k, v) =
+if erlang {
+ external fn do_take(List(k), Map(k, v)) -> Map(k, v) =
+  "maps" "with"
+}
+
+if javascript {
+ external fn do_take(List(k), Map(k, v)) -> Map(k, v) =
+  "../gleam_stdlib.js" "map_take"
+}
+
+/// Creates a new map from a pair of given maps by combining their entries.
+///
+/// If there are entries with the same keys in both maps the entry from the
+/// second map takes precedence.
+///
+/// ## Examples
+///
+///    > let a = from_list([#("a", 0), #("b", 1)])
+///    > let b = from_list([#("b", 2), #("c", 3)])
+///    > merge(a, b)
+///    from_list([#("a", 0), #("b", 2), #("c", 3)])
+///
+pub fn merge(into: Map(k, v), merge: Map(k, v)) -> Map(k, v) {
+  do_merge(into, merge)
+}
+
+if erlang {
+  external fn do_merge(into: Map(k, v), merge: Map(k, v)) -> Map(k, v) =
     "maps" "merge"
+}
 
-  external fn erl_delete(k, Map(k, v)) -> Map(k, v) =
+if javascript {
+  external fn do_merge(into: Map(k, v), merge: Map(k, v)) -> Map(k, v) =
+    "../gleam_stdlib.js" "map_merge"
+}
+
+/// Creates a new map from a given map with all the same entries except for the
+/// one with a given key, if it exists.
+///
+/// ## Examples
+///
+///    > delete([#("a", 0), #("b", 1)], "a")
+///    from_list([#("b", 1)])
+///
+///    > delete([#("a", 0), #("b", 1)], "c")
+///    from_list([#("a", 0), #("b", 1)])
+///
+pub fn delete(from map: Map(k, v), delete key: k) -> Map(k, v) {
+  do_delete(key, map)
+}
+
+if erlang {
+  external fn do_delete(k, Map(k, v)) -> Map(k, v) =
     "maps" "remove"
+}
 
-  /// Creates a new map from a given map with all the same entries except for the
-  /// one with a given key, if it exists.
-  ///
-  /// ## Examples
-  ///
-  ///    > delete([#("a", 0), #("b", 1)], "a")
-  ///    from_list([#("b", 1)])
-  ///
-  ///    > delete([#("a", 0), #("b", 1)], "c")
-  ///    from_list([#("a", 0), #("b", 1)])
-  ///
-  pub fn delete(from map: Map(k, v), delete key: k) -> Map(k, v) {
-    erl_delete(key, map)
-  }
+if javascript {
+  external fn do_delete(k, Map(k, v)) -> Map(k, v) =
+    "../gleam_stdlib.js" "map_remove"
+}
 
-  /// Creates a new map from a given map with all the same entries except any with
-  /// keys found in a given list.
-  ///
-  /// ## Examples
-  ///
-  ///    > drop([#("a", 0), #("b", 1)], ["a"])
-  ///    from_list([#("b", 2)])
-  ///
-  ///    > delete([#("a", 0), #("b", 1)], ["c"])
-  ///    from_list([#("a", 0), #("b", 1)])
-  ///
-  ///    > drop([#("a", 0), #("b", 1)], ["a", "b", "c"])
-  ///    from_list([])
-  ///
-  pub fn drop(from map: Map(k, v), drop disallowed_keys: List(k)) -> Map(k, v) {
-    list.fold(disallowed_keys, map, fn(key, acc) { delete(acc, key) })
-  }
+/// Creates a new map from a given map with all the same entries except any with
+/// keys found in a given list.
+///
+/// ## Examples
+///
+///    > drop([#("a", 0), #("b", 1)], ["a"])
+///    from_list([#("b", 2)])
+///
+///    > delete([#("a", 0), #("b", 1)], ["c"])
+///    from_list([#("a", 0), #("b", 1)])
+///
+///    > drop([#("a", 0), #("b", 1)], ["a", "b", "c"])
+///    from_list([])
+///
+pub fn drop(from map: Map(k, v), drop disallowed_keys: List(k)) -> Map(k, v) {
+  list.fold(disallowed_keys, map, fn(key, acc) { delete(acc, key) })
+}
 
-  /// Creates a new map with one entry updated using a given function.
-  ///
-  /// If there was not an entry in the map for the given key then the function
-  /// gets `Error(Nil)` as its argument, otherwise it gets `Ok(value)`.
-  ///
-  /// ## Example
-  ///
-  ///    > let increment = fn(x) {
-  ///    >   case x {
-  ///    >     Ok(i) -> i + 1
-  ///    >     Error(Nil) -> 0
-  ///    >   }
-  ///    > }
-  ///    > let map = from_list([#("a", 0)])
-  ///    >
-  ///    > update(map, "a" increment)
-  ///    from_list([#("a", 1)])
-  ///
-  ///    > update(map, "b" increment)
-  ///    from_list([#("a", 0), #("b", 0)])
-  ///
-  pub fn update(
-    in map: Map(k, v),
-    update key: k,
-    with fun: fn(Option(v)) -> v,
-  ) -> Map(k, v) {
-    map
-    |> get(key)
-    |> option.from_result
-    |> fun
-    |> insert(map, key, _)
-  }
+/// Creates a new map with one entry updated using a given function.
+///
+/// If there was not an entry in the map for the given key then the function
+/// gets `Error(Nil)` as its argument, otherwise it gets `Ok(value)`.
+///
+/// ## Example
+///
+///    > let increment = fn(x) {
+///    >   case x {
+///    >     Ok(i) -> i + 1
+///    >     Error(Nil) -> 0
+///    >   }
+///    > }
+///    > let map = from_list([#("a", 0)])
+///    >
+///    > update(map, "a" increment)
+///    from_list([#("a", 1)])
+///
+///    > update(map, "b" increment)
+///    from_list([#("a", 0), #("b", 0)])
+///
+pub fn update(
+  in map: Map(k, v),
+  update key: k,
+  with fun: fn(Option(v)) -> v,
+) -> Map(k, v) {
+  map
+  |> get(key)
+  |> option.from_result
+  |> fun
+  |> insert(map, key, _)
+}
 
-  fn do_fold(
-    list: List(#(k, v)),
-    initial: acc,
-    fun: fn(k, v, acc) -> acc,
-  ) -> acc {
-    case list {
-      [] -> initial
-      [#(k, v), ..tail] -> do_fold(tail, fun(k, v, initial), fun)
-    }
+fn do_fold(
+  list: List(#(k, v)),
+  initial: acc,
+  fun: fn(k, v, acc) -> acc,
+) -> acc {
+  case list {
+    [] -> initial
+    [#(k, v), ..tail] -> do_fold(tail, fun(k, v, initial), fun)
   }
+}
 
-  /// Combines all entries into a single value by calling a given function on each
-  /// one.
-  ///
-  /// Maps are not ordered so the values are not returned in any specific order. Do
-  /// not write code that relies on the order entries are used by this function
-  /// as it may change in later versions of Gleam or Erlang.
-  ///
-  /// # Examples
-  ///
-  ///    > let map = from_list([#("a", 1), #("b", 3), #("c", 9)])
-  ///    > fold(map, 0, fn(key, value, accumulator) { accumulator + value })
-  ///    13
-  ///
-  ///    > import gleam/string.{append}
-  ///    > fold(map, "", fn(key, value, accumulator) { append(accumulator, value) })
-  ///    "abc"
-  ///
-  pub fn fold(
-    over map: Map(k, v),
-    from initial: acc,
-    with fun: fn(k, v, acc) -> acc,
-  ) -> acc {
-    map
-    |> to_list
-    |> do_fold(initial, fun)
-  }
+/// Combines all entries into a single value by calling a given function on each
+/// one.
+///
+/// Maps are not ordered so the values are not returned in any specific order. Do
+/// not write code that relies on the order entries are used by this function
+/// as it may change in later versions of Gleam or Erlang.
+///
+/// # Examples
+///
+///    > let map = from_list([#("a", 1), #("b", 3), #("c", 9)])
+///    > fold(map, 0, fn(key, value, accumulator) { accumulator + value })
+///    13
+///
+///    > import gleam/string.{append}
+///    > fold(map, "", fn(key, value, accumulator) { append(accumulator, value) })
+///    "abc"
+///
+pub fn fold(
+  over map: Map(k, v),
+  from initial: acc,
+  with fun: fn(k, v, acc) -> acc,
+) -> acc {
+  map
+  |> to_list
+  |> do_fold(initial, fun)
 }
diff --git a/src/gleam_stdlib.js b/src/gleam_stdlib.js
index 652b7b5..0cb2417 100644
--- a/src/gleam_stdlib.js
+++ b/src/gleam_stdlib.js
@@ -258,3 +258,67 @@ export function regex_scan(regex, string) {
   });
   return List.fromArray(matches);
 }
+
+export function new_map() {
+  return new Map();
+}
+
+export function map_size(map) {
+  return map.size;
+}
+
+export function map_to_list(map) {
+  const result = [];
+  map.forEach(([a, b]) => result.push([JSON.parse(a), b]))
+}
+
+export function map_from_list(list) {
+  return new Map(list.map(([a, b]) => [JSON.stringify(a), b]));
+}
+
+export function map_has_key(k, map) {
+  return map.contains(JSON.stringify(k));
+}
+
+export function map_remove(k, map) {
+   new Map(map).remove(JSON.stringify(k));
+}
+
+export function map_filter(f, map) {
+  const result = new Map();
+  map.entries.forEach(([a, b]) => {
+    if (f(JSON.parse(a))) {
+      result.set(a, b);
+    }
+  })
+}
+
+export function map_get(from, get) {
+  from.get(JSON.stringify(get));
+}
+
+export function map_insert(key, value, map) {
+  return new Map(map).set(JSON.stringify(key), value);
+}
+
+export function map_keys(map) {
+  return [...map.keys()].map(key => JSON.parse(key));
+}
+
+export function map_values(map) {
+  return [...map.values()];
+}
+
+export function map_map_values(fn, map) {
+  const result = new Map();
+  map.forEach(([a, b]) => result.set(JSON.stringify(fn(JSON.parse(a))), b));
+}
+
+export function map_merge(into, merge) {
+  return new Map(...into, ...merge);
+}
+
+export function map_take(keys, map) {
+  const result = new Map();
+  keys.forEach(key => result.set(JSON.stringify(key), map.get(JSON.stringify(key))));
+}
\ No newline at end of file