Comparers

With comparators, you can abort the update propagation process if new and old data are equivalent

Shallow & Deep

Whatsup comparators are based on mutators and can be used more flexibly. If we use mobx we will do it like this:

const users = observable.array<User>([])
const admins = computed(() => users.filter((u) => u.isAdmin), {
    equals: comparer.shallow,
})

Here is whatsup way:

import { shallow } from 'whatsup/equals'

const users = array<User>([])
const admins = computed(() => shallow(users.filter((u) => u.isAdmin)))

Whatsup provides comparators as a separate library @whatsup/equals (shorthand whatsup/equals), so far it includes only shallow and deep, but in the future it will be replenished with the most popular ones

Custom comparator

You can easily create your own comparator

import { comparator } from 'whatsup'

const usersComparator = comparator<User>(
    (next, prev) =>
        Array.isArray(prev) &&
        prev.lenght === next.length &&
        prev.every((item, i) => item === next[i])
)
const users = array<User>([])
const admins = computed(() => usersComparator(users.filter((u) => u.isAdmin)))

To create a comparator, you only need a callback that takes a new and old value, compares and returns true or false