Remove a property in an object immutably

Question

I am using Redux. In my reducer I'm trying to remove a property from an object like this:

const state = {
    a: '1',
    b: '2',
    c: {
       x: '42',
       y: '43'
    },
}

And I want to have something like this without having to mutate the original state:

const newState = {
    a: '1',
    b: '2',
    c: {
       x: '42',
    },
}

I tried:

let newState = Object.assign({}, state);
delete newState.c.y

but for some reasons, it deletes the property from both states.

Could help me to do that?

Answer 1

How about using destructuring assignment syntax?

const original = {
  foo: 'bar',
  stack: 'overflow',
};

// If the name of the property to remove is constant
const { stack, ...withoutFirst } = original;
console.log(withoutFirst); // Will be { "foo": "bar" }

// If the name of the property to remove is from a variable
const key = 'stack'
const { [key]: value, ...withoutSecond } = original;
console.log(withoutSecond); // Will be { "foo": "bar" }

// To do a deep removal with property names from variables
const deep = {
  foo: 'bar',
  c: {
   x: 1,
   y: 2
  }
};

const parentKey = 'c';
const childKey = 'y';
// Remove the 'c' element from original
const { [parentKey]: parentValue, ...noChild } = deep;
// Remove the 'y' from the 'c' element
const { [childKey]: removedValue, ...childWithout } = parentValue;
// Merge back together
const withoutThird = { ...noChild, [parentKey]: childWithout };
console.log(withoutThird); // Will be { "foo": "bar", "c": { "x": 1 } }