Discussion on: 👋 Say Goodbye to Spread Operator: Use Default Composer

[aneesshameed]

merge and mergeWith is not doing what this post is about. Completely different

[René Kaesler]

I should have given an example. Normally I am using the following pattern, for default nested options:

const options = {
  b: 2,
  c: 3,
  nested: {
    e: 5,
    f: 6,
  },
};

const defaultOptions = {
  a: 1,
  b: "two",
  nested: {
    d: 4,
    e: "five",
  },
};

// this mutates `defaultOptions`:
const composedOptions = _.merge(defaultOptions, options);

// this preserves `defaultOptions`:
// const composedOptions = _.merge({}, defaultOptions, options);

console.log(composedOptions);
// => { a: 1, b: 2, c: 3, nested: { d: 4, e: 5, f: 6 }}

If you want to tweak the behaviour of value replacement differently for some values, you can use mergeWith. It's quite similar what the library is accomblishing.