memo

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Basic usage

Wrap a function with memo to get a function back that automagically returns values that have already been calculated.

import { memo } from 'radash'

const timestamp = memo(() => Date.now())

const now = timestamp()
const later = timestamp()

now === later // => true

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Expiration

You can optionally pass a ttl (time to live) that will expire memoized results. In versions prior to version 10, ttl had a value of 300 milliseconds if not specified.

import { memo, sleep } from 'radash'

const timestamp = memo(() => Date.now(), {
  ttl: 1000 // milliseconds
})

const now = timestamp()
const later = timestamp()

await sleep(2000)

const muchLater = timestamp()

now === later // => true
now === muchLater // => false

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Key Function

You can optionally customize how values are stored when memoized.

const timestamp = memo(({ group }: { group: string }) => {
  const ts = Date.now()
  return `${ts}::${group}`
}, {
  key: ({ group }: { group: string }) => group
})

const now = timestamp({ group: 'alpha' })
const later = timestamp({ group: 'alpha' })
const beta = timestamp({ group: 'beta' })

now === later // => true
beta === now // => false