diff --git a/src/FSharpPlus/Extensions/IList.fs b/src/FSharpPlus/Extensions/IList.fs
index f05ba64f5..641e1e74c 100644
--- a/src/FSharpPlus/Extensions/IList.fs
+++ b/src/FSharpPlus/Extensions/IList.fs
@@ -1,6 +1,5 @@
 namespace FSharpPlus
 
-#if !FABLE_COMPILER
 
 /// Additional operations IList<'T>
 [<RequireQualifiedAccess>]
@@ -9,9 +8,17 @@ module IList =
     open System.Collections.ObjectModel
     open System.Collections.Generic
 
+#if !FABLE_COMPILER
     /// <summary>Converts an IList to an IReadOnlyList (from System.Collections.Generic).</summary>
     /// <param name="source">The System.Collections.Generic.IList</param>
     /// <returns>The list converted to a System.Collections.Generic.IReadOnlyList</returns>
     let toIReadOnlyList (source: IList<_>) = ReadOnlyCollection source :> IReadOnlyList<_>
 
 #endif
+
+    let ofArray (source: 'T[]   ) = source                 :> IList<'T>
+    let ofList  (source: 'T list) = source |> Array.ofList :> IList<'T>
+    let ofSeq   (source: seq<'T>) = source |> Array.ofSeq  :> IList<'T>
+    let map  mapping (source: IList<'T>) = Seq.map  mapping source |> Seq.toArray :> IList<'U>
+    let iter mapping (source: IList<'T>) = Seq.iter mapping source
+
diff --git a/src/FSharpPlus/Extensions/IReadOnlyList.fs b/src/FSharpPlus/Extensions/IReadOnlyList.fs
index b0910bf58..e4ad6c2c2 100644
--- a/src/FSharpPlus/Extensions/IReadOnlyList.fs
+++ b/src/FSharpPlus/Extensions/IReadOnlyList.fs
@@ -8,7 +8,11 @@ module IReadOnlyList =
     #if !FABLE_COMPILER
     
     let ofArray (source: 'T array) = IList.toIReadOnlyList source
+    let ofList (source: 'T list) = source |> Array.ofList |> IList.toIReadOnlyList
+    let ofSeq  (source: seq<'T>) = source |> Array.ofSeq  |> IList.toIReadOnlyList
+
     #endif
+
     let toArray (source: IReadOnlyList<'T>) = Array.ofSeq source
 
     #if !FABLE_COMPILER
@@ -19,8 +23,13 @@ module IReadOnlyList =
         if 0 <= i && i < source.Count then
             source |> Array.ofSeq |> setNth i value |> ofArray |> Some
         else None
+    
+    let map mapping (source: IReadOnlyList<'T>) : IReadOnlyList<'U> = Seq.map mapping source |> Seq.toArray |> IList.toIReadOnlyList
+    
     #endif
 
     let tryItem i (source: IReadOnlyList<_>) =
         if 0 <= i && i < source.Count then Some source.[i]
-        else None
\ No newline at end of file
+        else None
+
+    let iter mapping (source: IReadOnlyList<'T>) = Seq.iter mapping source
\ No newline at end of file