What is logged when accessing a[b] after setting values for a[b] and a[c]?

When accessing a[b] after setting values for a[b] and a[c], if the context indicates that both properties exist and have been successfully assigned values, then accessing a[b] will return the value associated with that key.

In this scenario, if you have assigned the value 456 to a[b], then it is that value that will be logged when you access a[b]. This is because JavaScript objects allow for dynamic assignment of properties, so when you do a[b] = 456, you are creating or updating a property in the object a with the key defined by the variable b. Thus, when you later access a[b], it retrieves the value 456.

For clarity, if a[b] had not been assigned any value prior to that access or if the variable b did not correspond to any valid property of the object a, different outcomes might occur, such as receiving undefined. However, since the question specifies that values have already been set for a[b], the expected outcome of accessing a[b] would indeed yield 456, assuming that the value was explicitly defined as such.