Fix Object.assign example

The Object.assign example is currently incorrect.

function createMenu(config) {
  Object.assign(config, {
    title: 'Foo',
    body: 'Bar',
    buttonText: 'Baz',
    cancellable: true
  });
}

createMenu({ title: 'Not Foo' });

The title property will always be set to 'Foo'!

I was going to make a PR with a fix, but the approach really depends on whether the mutation of config is desirable.

How I would do it (this does not behave identically to the “bad” example):

function createMenu(config) {
  // makes a copy of `config`, with default values
  config = Object.assign({
    title: 'Foo',
    body: 'Bar',
    buttonText: 'Baz',
    cancellable: true
  }, config);
}

How you could do it with mutation (this is identical to the “bad” example):

function createMenu(config) {
  // mutates `config`, setting default values
  Object.assign(config, Object.assign({
    title: 'Foo',
    body: 'Bar',
    buttonText: 'Baz',
    cancellable: true
  }, config));
}

[connec]

@rkichenama that example does not work because config has already mutated when the ‘overrides’ are applied:

let config = { key: 'override' }
Object.assign(config, { key: 'default' }, config)
console.log(config.key) // default

Hence the need for an additional Object.assign.

@kwelch that option is equivalent to the non-mutating version I specified - the defaults are already in a new object, so merging them into another new object is redundant.

---

Anyway, looks like this was fixed in https://github.com/ryanmcdermott/clean-code-javascript/commit/d00ca4c70c97076b9678c193b125fdf9b810b89e with @kwelch’s version.

[kwelch]

@connec I agree ours are the same, I just prefer not editing parameters if you are attempting to be functional.