Discover functional programming patterns with RamdaJS. Learn about pure functions, currying, and point-free style while deepening your knowledge of map, filter, and reduce methods.

We know the functional programming (FP) hype train's been riding strong the past few years, especially in the JavaScript community. We extol FP in countless books, videos, and blog posts, with no sign of slowing down.

As a result this course isn't to convince you, today's JS developer, of how awesome FP is. I'm simply sharing some popular patterns using Ramda, an FP library that I've blogged on many times.

Before going through them, though, we will lay the groundwork with concepts like pure functions, currying, and point-free style.

You're already doing FP through map, filter, reduce, and Lodash, so why not dive a bit deeper and see if you like it down here?

Functional Programming Patterns With RamdaJS!

Given a maximum price and menu, return the 3 top-rated meals for that price or less.

**Usage**
```javascript
// top 3 meals for $12 or less
const best3Meals = getTop3MealsFor(12, menu);

/*
[{
  name: 'Lamb Gyro',
  price: 11.86,
  rating: 4.9
}, {
  name: 'House Salad',
  price: 9.00,
  rating: 4.65
}, {
  name: 'Gigantus Fries',
  price: 11.86,
  rating: 4.5
}]
*/
```

Your solution must be point-free.

Notice how the `menu` parameter's supplied last, aligning with Ramda's "data-last" pattern. This lets you compose `getTop3MealsFor` with other functions to manipulate `menu` in different ways.

const firstPerfectMeal = pipe(
  getTop3MealsFor(20),
  filter(
    both(isVegetarian, isLactoseFree)
  ),
  head
);


This finds the best $20 or less vegetarian/lactose-free meal. All it needs is a `menu` parameter and off it goes!

export default [{
  name: 'Lamb Gyro',
  price: 11.86,
  rating: 3.31
}, {
  name: 'Chicken Gyro',
  price: 11.48,
  rating: 3.84
}, {
  name: 'Mixed Gyro',
  price: 11.69,
  rating: 4.81
}, {
  name: 'Jumbo Lamb',
  price: 12.31,
  rating: 2.32
}, {
  name: 'Lamb Kebab',
  price: 8.85,
  rating: 4.82
}, {
  name: 'Jumbo Mixed',
  price: 14.96,
  rating: 3.37
}, {
  name: 'Chicken Wings',
  price: 11.17,
  rating: 3.56
}, {
  name: 'Biggie Fries',
  price: 14.36,
  rating: 3.86
}, {
  name: 'Medium Fries',
  price: 10.36,
  rating: 4.96
}, {
  name: 'Medium Curly Fries',
  price: 10.37,
  rating: 2.52
}, {
  name: 'Biggie Curly Fries',
  price: 15.07,
  rating: 3.73
}, {
  name: 'House Salad',
  price: 11.39,
  rating: 4.86
}, {
  name: 'Apartment Salad',
  price: 14.38,
  rating: 2.80
}, {
  name: 'Steak',
  price: 12.50,
  rating: 4.06
}, {
  name: 'Shrimp Gyro',
  price: 14.57,
  rating: 3.48
}];


import {} from 'ramda';
import menu from './menu';

const getTop3MealsFor = () => {};


Write a point-free function to get the 3 top-rated meals <= a given price.

Introduction

Pure Functions

Higher-Order Functions

Function Composition

Currying

Pipe and Compose

Sorting

Conditional Logic

Using What We've Learned

Functors

Lenses

Lenses Exercises

Building a Wikipedia Search

Closing Comments

Bang for Your Buck: Exercise