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p-async-cache

1.0.3
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  • License MIT

Cache the promise lookups and avoid fetching the same thing more than necessary

Package Exports

  • p-async-cache

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (p-async-cache) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

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p-async-cache

Cache the promise lookups and avoid fetching the same thing more than necessary.

Install

$ npm install p-async-cache --save

Usage

import PAC from 'p-async-cache'

let counter = 0
const cache = new PAC({
  async load (userId) {
    counter ++
    return await getUserFromRemote(userId)
  }
})

function get () {
  cache.get(123).then(({value}) => {
    console.log(value, counter)
  })
}

get()
get()

// [object User] 1
// [object User] 1 (The counter still be 1)

new AC(options)

  • options Object=
    • stale Boolean whether allow stale value
    • stringify function()=JSON.stringify method to serialize the params to a cache key.
    • load AsyncFunction(...params)|function(...params):Promise|function(...params) accepts a normal synchronous function, a function that returns a promise, or an async function, and the params will be the parameters of the .get(...params) method.
    • other options that lru-cache supports

Example for options.stale

import delay from 'delay'

const cache = new AC({
  stale: true,
  maxAge: 100,
  load (a, b) {
    return delay(1).then(() => a + b)
  }
})

cache.get(1, 2)
.then(({value, stale}) => {
  console.log(value)      // 3
  console.log(stale)      // false

  // Delay a timespan which is bigger than `maxAge`
  return delay(101).then(() => cache.get(1, 2))
})
.then(({value, stale}) => {
  console.log(value)      // 3
  console.log(stale)      // true (the value is stale)

  return delay(10).then(() => cache.get(1, 2))
})
.then(({value, stale}) => {
  console.log(value)      // 3
  console.log(stale)      // false (if the value is found as stale, it will refresh the value in the background)
})

.get(...params)

  • params any that will be passed into options.load(...params)

Returns Promise

Lookup the value in the cache,

  • if found, then return.
  • if not found,
    • if allow stale values, and the value is stale, then return the value, and refresh value in background.
    • otherwise, load the value with load(...params)

Other methods of lru-cache

  • .reset()
  • .has(...params)
  • .peek(...params)
  • .del(...params)

License

MIT