Is there a lodash/fp equivalent of Ramda's 'evolve' function?

Question

Looking for a lodash equivalent of Ramda's evolve :

const transformForDisplay = (item) => {
  const transform = {
    body: truncate({ length: 100 }),
    title: truncate({ length: 50 })
  }

  return R.evolve(transform, item)
}

Which returns an object containing all of the original fields from 'item' but truncating the 'body' and 'title' fields if they exist.

Edit: this works. Anything more pithy?

const transformForDisplay = (item) => {
  const transform = {
    body: truncate,
    title: truncate
  }

  const mapValuesWithKey = _.mapValues.convert({ cap: false })
  return mapValuesWithKey((x, key) => transform[key] ? transform[key](x) : x)(item)
}

Answer 1

I wasn't able to find any built-in equivalent. Here's how you might implement evolve yourself.

It's pretty much what you already had, except I used _.getOr to avoid having to repeat transform[key] , and I added a recursive call to evolve when necessary.

 // Implementation const mapValuesWithKey = _.mapValues.convert({cap: false}); function evolve(transformations) { return item => mapValuesWithKey((value, key) => { const transformation = _.getOr(_.identity)(key)(transformations); const type = typeof transformation; return type === 'function' ? transformation(value) : transformation && type === 'object' ? evolve(transformation)(value) : value; })(item); } // Example const tomato = { firstName: ' Tomato ', data: {elapsed: 100, remaining: 1400}, id: 123 }; const transformations = { firstName: _.trim, lastName: _.trim, // Will not get invoked. data: {elapsed: _.add(1), remaining: _.add(-1)}, id: null, // Will have no effect. } const result = evolve(transformations)(tomato); console.log(result); 

 <script src="https://cdn.jsdelivr.net/lodash/4.13.1/lodash.min.js"></script> <script src="https://cdn.jsdelivr.net/lodash/4.13.1/lodash.fp.min.js"></script> 

Answer 2

Just tried to use more lodash functions:

const evolve = _.curry((transformations, item) =>
    _.mapValues.convert({ cap: false })((value, key) => {
        const transformation = _.propOr(identity, key, transformations);

        return _.cond([
            [_.isFunction, t => t(value)],
            [_.isObject, t => evolve(t, value)],
            [_.T, _.always(value)],
        ])(transformation);
    }, item)
);