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Functional Programming Patterns With RamdaJS!

Sort Functions

Overview of Ramda's sorting functions. (4 min. read)

We'll cover the following...

Sort Functions

The native sort is destructive, meaning it mutates the array.

Javascript (babel-node)
const nums = [3, 2, 4, 1];
const result = nums.sort((a, b) => a - b)
console.log({ nums, result });

Ramda provides a non-destructive sort function.

Javascript (babel-node)
import { sort } from 'ramda';
const nums = [3, 2, 4, 1];
const result = sort((a, b) => a - b, nums);
console.log({ nums, result });

sortBy applies a function to your values before comparing them. Sorting by absolute value, for example, is trivial now.

Javascript (babel-node)
import { sortBy } from 'ramda';
const result = sortBy(Math.abs, [-100, 1, -50, 0]);
console.log({ result });

If you’d like to sort by multiple criteria, sortWith is your friend. This example sorts people by their age, then name.

Javascript (babel-node)
import { ascend, prop, sortWith } from 'ramda';
const people = [{
  name: 'Bobo',
  age: 25
}, {
  name: 'Cam',
  age: 25
}, {
  name: 'Al',
  age: 29
}];
const result = sortWith([
  ascend(prop('age')),
  ascend(prop('name'))
], people);
console.log({ result });

Ramda’s ascend functions wraps around prop('age'), telling it “Sort by age, ascending (smallest first)”.

Javascript (babel-node)
ascend(prop('age'))

Same with prop('name'): “Sort by name, ascending (A, B, C, D…).”

Javascript (babel-node)
ascend(prop('name'))

So if they’re the same age, sortWith will then sort by name.

For the opposite effect, use descend.

Javascript (babel-node)
import { descend, prop, sortWith } from 'ramda';
const people = [{
  name: 'Bobo',
  age: 25
}, {
  name: 'Cam',
  age: 25
}, {
  name: 'Al',
  age: 29
}];
const result = sortWith([
  descend(prop('age')),
  descend(prop('name'))
], people);
console.log({ result });

Now people's sorted in opposite order.