const maps have some redundancy:

const {'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5}

--->

C.List_8xz = Isolate.makeConstantList(["a", "b", "c", "d", "e"]);
C.Map_8x6Jr = new H.ConstantStringMap(5, {a: 1, b: 2, c: 3, d: 4, e: 5}, C.List_8xz);

1. The key names are repeated. 2. The length is redundant with respect to the list.

Instead of parsing and constructing the object literal, the JS code could call a helper that takes a keys list and a values list.

C.List_8xz = Isolate.makeConstantList(["a", "b", "c", "d", "e"]);
C.Map_8x6Jr = Isolate.makeConstantStringMap(C.List_8xz, [1, 2, 3, 4, 5]);

The space saving is roughly the accumulated length of the keys, provided 'makeConstantStringMap' is minified.