Recursive "merge" or "extend" with Ramda?

Question

I'm trying to find an equivalent function to Lodash's merge using Ramda that does a recursive object key-based "merge" or "extend". The behavior is similar to the following:

let merged = R.someMethod(
  { name: 'Matt', address: { street: 'Hawthorne', number: 22, suffix: 'Ave' }},
  { address: { street: 'Pine', number: 33 }}
);

console.log(merged);

// => { name: 'Matt', address: { street: 'Pine', number: 33, suffix: 'Ave' }}

I noticed in the following pull request that R.set was briefly introduced, but then rolled back soon thereafter. Has this functionality been captured by the Ramda library since?

Is this functionality available in Ramda?

Answer 1

A relatively simple recursive function can be created using R.mergeWith.

function deepMerge(a, b) {
  return (R.is(Object, a) && R.is(Object, b)) ? R.mergeWith(deepMerge, a, b) : b;
}

deepMerge({ name: 'Matt', address: { street: 'Hawthorne', number: 22, suffix: 'Ave' }},
          { address: { street: 'Pine', number: 33 }});

//=> {"address": {"number": 33, "street": "Pine", "suffix": "Ave"}, "name": "Matt"}

Answer 2

Ramda does not include such a function at the moment.

There have been several attempts to create one, but they seem to founder on the notion of what's really required of such a function.

Feel free to raise an issue if you think it's worth adding.

Update

(Two years later.) This was eventually added, in the form of several functions: mergeDeepLeft, mergeDeepRight, mergeDeepWith, and mergeDeepWithKey.

Answer 3

Ramda now has several merge functions: mergeDeepLeft, mergeDeepRight, mergeDeepWith, mergeDeepWithKey.

Answer 4

const { unapply, mergeDeepRight, reduce } = R
const mergeDeepRightAll = unapply(reduce(mergeDeepRight, {}))

console.log(mergeDeepRightAll({a:1, b: {c: 1}},{a:2, d: {f: 2}},{a:3, b: {c:3}}))

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