Data-Helpers

Useful functions for working with array methods, such as map(), reduce(), filter(), and sort()

by

Accepts one or more sorting conditions, expressed as string or function. If passed a string, the string should represent the property of the object to sort by:

cashBackCards.sort(by('rating'))

/* [
{rating: 3.7, name: "Capital One® Quicksilver®...", bank: "Capital One®"}
{rating: 3.7, name: "Discover it® Cash Back", bank: "Discover®"}
{rating: 3.7, name: "Capital One® Savor® Cash ...", bank: "Capital One®"}
{rating: 4.4, name: "Bank of America® Cash Rew...", bank: "Bank of America®"}
] */

By default, results are in ascending order. strings can be prefixed with a '<' or '>' to force the sort to be in ascending or descending order respectively

cashBackCards.sort(by('>rating'))

/* [
  {rating: 4.4, name: "Bank of America® Cash Rew...", bank: "Bank of America®"}
  {rating: 3.7, name: "Capital One® Quicksilver®...", bank: "Capital One®"}
  {rating: 3.7, name: "Discover it® Cash Back", bank: "Discover®"}
  {rating: 3.7, name: "Capital One® Savor® Cash ...", bank: "Capital One®"}
] */

The value we pass as a string can also contain an object chain

cashBackCards.sort(by('<bank.length'))

/* [
  {rating: 3.7, name: "Discover it® Cash Back", bank: "Discover®"}
  {rating: 3.7, name: "Capital One® Quicksilver®...", bank: "Capital One®"}
  {rating: 3.7, name: "Capital One® Savor® Cash ...", bank: "Capital One®"}
  {rating: 4.4, name: "Bank of America® Cash Rew...", bank: "Bank of America®"}
] */

We can also create a custom function to sort by. The sorting function should accept two objects, compare them, and return -1 or 1 if the condition was passed. In this way, any valid sorting function for Array.prototype.sort() is valid for by()

// sort by the number of registered trademark symbols in the name
function registeredCount(cardA, cardB) {
  const a = cardA.name.split('®').length
  const b = cardB.name.split('®').length

  if (a > b) return 1
  if (a < b) return -1
  return 0
}

cashBackCards.sort(by(registeredCount))
/* [
  {rating: 3.7, name: "Discover it® Cash Back", bank: "Discover®"}
  {rating: 4.4, name: "Bank of America® Cash Rew...", bank: "Bank of America®"}
  {rating: 3.7, name: "Capital One® Quicksilver®...", bank: "Capital One®"}
  {rating: 3.7, name: "Capital One® Savor® Cash ...", bank: "Capital One®"}
] */

This is useful because we can assign multiple sorting conditions to be executed in order. The following example sorts first by our custom function and second by the card name

// sort by the number of registered trademark symbols in the name
function registeredCount(cardA, cardB) {
  const a = cardA.name.split('®').length
  const b = cardB.name.split('®').length

  if (a > b) return 1
  if (a < b) return -1
  return 0
}

cashBackCards.sort(by(registeredCount, 'name'))
/* [
  {rating: 4.4, name: "Bank of America® Cash Rew...", bank: "Bank of America®"}
  {rating: 3.7, name: "Discover it® Cash Back", bank: "Discover®"}
  {rating: 3.7, name: "Capital One® Quicksilver®...", bank: "Capital One®"}
  {rating: 3.7, name: "Capital One® Savor® Cash ...", bank: "Capital One®"}
] */

You can use multiple string arguments as well:

cashBackCards.sort(by('>rating', '<name'))
/* [
  {rating: 4.4, name: "Bank of America® Cash Rew...", bank: "Bank of America®"}
  {rating: 3.7, name: "Capital One® Quicksilver®...", bank: "Capital One®"}
  {rating: 3.7, name: "Capital One® Savor® Cash ...", bank: "Capital One®"}
  {rating: 3.7, name: "Discover it® Cash Back", bank: "Discover®"}
] */