Каково различие между CIL и MSIL (IL)?

const obj1 = { "-L1Rm6VbfLLyFJ3Qi6K": {city: "Tokyo", date: "26-08-2004" } }

const obj2 = {}

for (const id in obj1) {
  Object.assign(obj2, { id, ...obj1[id] })
}

console.log(obj2);

const obj1 = { "-L1Rm6VbfLLyFJ3Qi6K": {city: "Tokyo", date: "26-08-2004" } }

for (const id in obj1) {
   Object.assign(obj1, { id, ...obj1[id] })
   delete obj1[id];
}

console.log(obj1);