Another update from ingydotnet^djgoku

Task/Y-combinator/JavaScript/y-combinator-7.js

@@ -0,0 +1,9 @@
+let
+    polyfix= // A version that takes an array instead of multiple arguments would simply use l instead of (...l) for parameter
+        (...l)=>(
+            (f=>f(f))
+            (g=>l.map(f=>(...x)=>f(...g(g))(...x)))),
+    [even,odd]= // The new destructive assignment syntax for arrays
+        polyfix(
+            (even,odd)=>n=>(n===0)||odd(n-1),
+            (even,odd)=>n=>(n!==0)&&even(n-1));