2691. Immutability Helper π
Description
Creating clones of immutable objects with minor alterations can be a tedious process. Write a class ImmutableHelper
that serves as a tool to help with this requirement. The constructor accepts an immutable object obj
which will be a JSON object or array.
The class has a single method produce
which accepts a function mutator
. The function returns a new object which is similar to the original except it has those mutations applied.
mutator
accepts a proxied version of obj
. A user of this function can (appear to) mutate this object, but the original object obj
should not actually be effected.
For example, a user could write code like this:
const originalObj = {"x": 5}; const helper = new ImmutableHelper(originalObj); const newObj = helper.produce((proxy) => { proxy.x = proxy.x + 1; }); console.log(originalObj); // {"x": 5} console.log(newObj); // {"x": 6}
Properties of the mutator
function:
- It will always return
undefined
. - It will never access keys that don't exist.
- It will never delete keys (
delete obj.key
) - It will never call methods on a proxied object (
push
,shift
, etc). - It will never set keys to objects (
proxy.x = {}
)
Note on how the solution will be tested: the solution validator will only analyze differences between what was returned and the original obj
. Doing a full comparison would be too computationally expensive. Also, any mutations to the original object will result in a wrong answer.
Example 1:
Input: obj = {"val": 10}, mutators = [ proxy => { proxy.val += 1; }, proxy => { proxy.val -= 1; } ] Output: [ {"val": 11}, {"val": 9} ] Explanation: const helper = new ImmutableHelper({val: 10}); helper.produce(proxy => { proxy.val += 1; }); // { "val": 11 } helper.produce(proxy => { proxy.val -= 1; }); // { "val": 9 }
Example 2:
Input: obj = {"arr": [1, 2, 3]} mutators = [ proxy => { proxy.arr[0] = 5; proxy.newVal = proxy.arr[0] + proxy.arr[1]; } ] Output: [ {"arr": [5, 2, 3], "newVal": 7 } ] Explanation: Two edits were made to the original array. The first element in the array was to set 5. Then a new key was added with a value of 7.
Example 3:
Input: obj = {"obj": {"val": {"x": 10, "y": 20}}} mutators = [ proxy => { let data = proxy.obj.val; let temp = data.x; data.x = data.y; data.y = temp; } ] Output: [ {"obj": {"val": {"x": 20, "y": 10}}} ] Explanation: The values of "x" and "y" were swapped.
Constraints:
2 <= JSON.stringify(obj).length <= 4 * 105
mutators
is an array of functionstotal calls to produce() < 105
Solutions
Solution 1
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