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Memoize functions - An optimization used to speed up consecutive function calls by caching the result of calls with identical input
$ npm install --save mem
const mem = require('mem');
let i = 0;
const counter = () => ++i;
const memoized = mem(counter);
memoized('foo');
//=> 1
// cached as it's the same arguments
memoized('foo');
//=> 1
// not cached anymore as the arguments changed
memoized('bar');
//=> 2
memoized('bar');
//=> 2
const mem = require('mem');
let i = 0;
const counter = () => Promise.resolve(++i);
const memoized = mem(counter);
memoized().then(a => {
console.log(a);
//=> 1
memoized().then(b => {
// the return value didn't increase as it's cached
console.log(b);
//=> 1
});
});
const mem = require('mem');
const got = require('got');
const memGot = mem(got, {maxAge: 1000});
memGot('sindresorhus.com').then(() => {
// this call is cached
memGot('sindresorhus.com').then(() => {
setTimeout(() => {
// this call is not cached as the cache has expired
memGot('sindresorhus.com').then(() => {});
}, 2000);
});
});
Type: Function
Function to be memoized.
Type: number
Default: Infinity
Milliseconds until the cache expires.
Type: Function
Determines the cache key for storing the result based on the function arguments. By default, if there's only one argument and it's a primitive, it's used directly as a key, otherwise it's all the function arguments JSON stringified as an array.
You could for example change it to only cache on the first argument x => JSON.stringify(x)
.
Type: Object
Default: new Map()
Use a different cache storage. Must implement the following methods: .has(key)
, .get(key)
, .set(key, value)
, and optionally .clear()
. You could for example use a WeakMap
instead.
Clear all cached data of a memoized function.
Type: Function
Memoized function.
If you want to know how many times your cache had a hit or a miss, you can make use of stats-map as a replacement for the default cache.
const mem = require('mem');
const StatsMap = require('stats-map');
const got = require('got');
const cache = new StatsMap();
const memGot = mem(got, {cache});
memGot('sindresorhus.com')
.then(() => memGot('sindresorhus.com'))
.then(() => memGot('sindresorhus.com'));
console.log(cache.stats);
//=> {hits: 2, misses: 1}
MIT © Sindre Sorhus