sort-lib

A small set of utilities for writing more readable sort functions.

• Tiny - almost fits in a tweet, tree-shakable.
• Typescript
• ES modules

If you're like me, you probably always need to look up how to sort an array in JS. ("How do you sort strings again?", "Is it first argument minus second argument for descending, or the other way around?") This module is meant to solve that problem, while making the code more readable in the process.

Installation

npm install sort-lib

Usage

import { desc, byNum } from 'sort-lib';

[
  { age: 25 },
  { age: 10 },
  { age: 42 }
]
  // Sort descending by number `.age`
  .sort(desc(byNum(value => value.age)))

/*
[
  { age: 42 },
  { age: 25 },
  { age: 10 }
]
*/

Functions

asc / desc

Wrap the sort function with asc or desc to set the sort direction. If you do not use this function, sorting will always happen in the ascending direction.

byNum(numberGetter)

Creates a sort function that can be used to sort a number. You have to pass in a function that returns a number given a value in the array - this number is what the sorting is performed on. byNum returns a sort function.

byDate(dateGetter)

Like byNum, but for date objects. Pass in a function that returns a date given a value in the array. Returns a sort function.

Internally, compares dates by calling .getTime() on the date objects.

[
  { dateOfBirth: new Date('2000-01-01') },
  { dateOfBirth: new Date('2020-01-01') },
  { dateOfBirth: new Date('1970-01-01') }
]
  // Sort ascending by date `.dateOfBirth`
  .sort(asc(byDate(x => x.dateOfBirth)))

/*
[
  { dateOfBirth: new Date('1970-01-01') },
  { dateOfBirth: new Date('2000-01-01') },
  { dateOfBirth: new Date('2020-01-01') }
]
*/

byString(stringGetter)

Like byNum and byDate above, but for strings. Pass in a function that returns a string given a value in the array. Returns a sort function.

Internally, compares strings using the .localeCompare method.

[
  { name: 'Bob' },
  { name: 'Alice' },
  { name: 'Charlie' }
]
  // Sort descending by string `.name`
  .sort(desc(byString(x => x.name)))

/*
[
  { name: 'Charlie' },
  { name: 'Bob' },
  { name: 'Alice' }
]
*/

Tips

• Define a function called prop, or use one from a library like ramda for even more point-free code:

  const prop = <T>(key: keyof T) => (obj: T) => obj[key];
  
  [{ age: 42 }, { age: 10 }]
    .sort(desc(byNum(prop('age'))))

• If your array only contains primitives, you might want to define a function called identity (or use the one from ramda)

  const identity = <T>(x: T) => x;
  
  ['Alice', 'Bob'].sort(desc(byString(identity)))