[Ramda] Get a List of Unique Values From Nested Arrays with Ramda (flatMap --> Chain)

In this lesson, we'll grab arrays of values from other arrays, resulting in a nested array. From there, we'll look at multiple ways to flatten the array structure using composition with

map

and

unnest

and then refactoring to use

chain

, AKA

flatMap

. Finally, we'll add Ramda's

uniq

function to remove duplicate values.

const R = require('ramda');

const {map, chain, prop, pluck, compose, uniq, tap, curry} = R;

const product = {
name: "Sample Data",
sizes: [
{
name: "L",
colors: [
{
name: "Red"
},
{
name: "Blue"
}
]
},
{
name: "M",
colors: [
{
name: "Green"
},
{
name: "Yellow"
}
]
},
{
name: "S",
colors: [
{
name: "Orange"
},
{
name: "Purple"
},
{
name: "Blue"
}
]
}
]
};

const log = curry((desc, x) => R.tap(() => console.log(desc, JSON.stringify(x, null, 2)), x));

// Target: to get unique array of color from product object

const sizes = prop('sizes');
const getColors = chain(prop('colors')); // flatMap, get colors props from array of objects
const getColorNames = pluck('name'); // get name prop from array of objects
const res = compose(
uniq,
log("after name"),
getColorNames,
log("after colors"),
getColors,
log("after sizes"),
sizes
)(product);

console.log(JSON.stringify(res, null, 2));
/*
* after sizes [
{
"name": "L",
"colors": [
{
"name": "Red"
},
{
"name": "Blue"
}
]
},
{
"name": "M",
"colors": [
{
"name": "Green"
},
{
"name": "Yellow"
}
]
},
{
"name": "S",
"colors": [
{
"name": "Orange"
},
{
"name": "Purple"
},
{
"name": "Blue"
}
]
}
]
after colors [
{
"name": "Red"
},
{
"name": "Blue"
},
{
"name": "Green"
},
{
"name": "Yellow"
},
{
"name": "Orange"
},
{
"name": "Purple"
},
{
"name": "Blue"
}
]
after name [
"Red",
"Blue",
"Green",
"Yellow",
"Orange",
"Purple",
"Blue"
]
[
"Red",
"Blue",
"Green",
"Yellow",
"Orange",
"Purple"
]
* */