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Functional Programming Patterns With RamdaJS!

Fix the Flavors: Solution Review

Explore how to apply RamdaJS lenses for targeted data transformations. Learn to combine lensPath with map, over, and view functions to uppercase and enhance flavor values efficiently, minimizing code complexity through function composition and helper functions.

We'll cover the following...

We know from the last exercise that lensPath is the easiest way to focus on everyone’s favorite flavor.

Javascript (babel-node)
import { lensPath } from 'ramda';
const favoriteFlavor = lensPath([
	'interests',
	'foods',
	'sweets',
	'iceCream',
	'favoriteFlavor'
]);

Then combining it with map and view will fetch them.

Javascript (babel-node)
import { lensPath, map, view } from 'ramda';
import employees from './employees.json';
const favoriteFlavor = lensPath([
	'interests',
	'foods',
	'sweets',
	'iceCream',
	'favoriteFlavor'
]);
const result = map(view(favoriteFlavor), employees);
console.log({ result });

But now there’s work to do in between. Before view, we need a setter lens. Unfortunately set is only good for static values.

Javascript (babel-node)
set(favoriteFlavor, 'Chocolate');

Uppercasing Flavors

over, however, lets us set using functions! We can use Ramda’s toUpper function to uppercase all the flavors.

Javascript (babel-node)
import { lensPath, map, over, toUpper, view } from 'ramda';
import employees from './employees.json';
const favoriteFlavor = lensPath([
	'interests',
	'foods',
	'sweets',
	'iceCream',
	'favoriteFlavor'
]);
const modifiedFlavors = map(over(favoriteFlavor, toUpper), employees);
const result = map(view(favoriteFlavor), modifiedFlavors);
console.log({ result });

Again, it’s a list of employees so map's necessary here. over focuses on an object using the favoriteFlavor lens, and uppercases its value.

That returns a new object with the modified flavors.

Passing that new array to map(view) returns the capitalized flavors.

Appending to Flavors

But wait there’s more! We must also append “IS A GREAT FLAVOR” to each of them.

We could combine that with toUpper using good ol’ pipe.

Javascript (babel-node)
import { lensPath, map, pipe, over, toUpper, view } from 'ramda';
import employees from './employees.json';
const favoriteFlavor = lensPath([
	'interests',
	'foods',
	'sweets',
	'iceCream',
	'favoriteFlavor'
]);
const modifiedFlavors = map(over(favoriteFlavor, pipe(toUpper, (flavor) => `${flavor} IS A GREAT FLAVOR`)), employees);
const result = map(view(favoriteFlavor), modifiedFlavors);
console.log({ result });

This does the job, but not very eloquently. Look at that nesting!

Javascript (babel-node)
const modifiedFlavors = map(over(favoriteFlavor, pipe(toUpper, (flavor) => `${flavor} IS A GREAT FLAVOR`)), employees);

Let’s create a helper function, emphasize.

Javascript (babel-node)
import { lensPath, map, pipe, over, toUpper, view } from 'ramda';
import employees from './employees.json';
const favoriteFlavor = lensPath([
	'interests',
	'foods',
	'sweets',
	'iceCream',
	'favoriteFlavor'
]);
const emphasize = pipe(
  toUpper,
  (flavor) => `${flavor} IS A GREAT FLAVOR`
);
const modifiedFlavors = map(over(favoriteFlavor, emphasize), employees);
const result = map(view(favoriteFlavor), modifiedFlavors);
console.log({ result });

Good, let’s go a step further.

Remember that lenses compose too. We don’t need to separate them and call map twice!

Javascript (babel-node)
import { lensPath, map, pipe, over, toUpper, view } from 'ramda';
import employees from './employees.json';
const favoriteFlavor = lensPath([
	'interests',
	'foods',
	'sweets',
	'iceCream',
	'favoriteFlavor'
]);
const emphasize = pipe(
  toUpper,
  (flavor) => `${flavor} IS A GREAT FLAVOR`
);
const emphasizeFlavor = pipe(
  over(favoriteFlavor, emphasize),
  view(favoriteFlavor)
);
const emphasizeFlavors = map(emphasizeFlavor);
const result = emphasizeFlavors(employees);
console.log({ result });