Remove a property in an object immutably

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?

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 } }

I find ES5 array methods like filter, map and reduce useful because they always return new arrays or objects. In this case I'd use Object.keys to iterate over the object, and Array#reduce to turn it back into an object.

return Object.assign({}, state, {
    c: Object.keys(state.c).reduce((result, key) => {
        if (key !== 'y') {
            result[key] = state.c[key];
        }
        return result;
    }, {})
});

You can use _.omit(object, [paths]) from lodash library

path can be nested for example: _.omit(object, ['key1.key2.key3'])