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Functional Programming Patterns With RamdaJS!

Sort Functions

Explore how to use RamdaJS to perform non-destructive sorting on arrays. Understand how sortBy applies functions before comparisons, and how sortWith enables sorting by multiple criteria such as age and name, ascending or descending.

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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.