memo

307 bytes

Usage

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

import * as _ from 'radashi'

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

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

now === later // => true

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 * as _ from 'radashi'

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

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