@starryinternet/map-memo

map-memo

Generic memoization using Map and WeakMap.

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Installing

npm install --save @starryinternet/map-memo

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What/Why?

Memoization in JavaScript has typically been limited to arguments with primitive values, or by utilizing hacks such as stringifying objects.

By storing arguments using a series of nested cache objects backed by Map and WeakMap, map-memo is able to memoize functions with any argument types.

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Example

'use strict';

const memoize = require('@starryinternet/map-memo');

function loop( fn, n ) {
  let v;

  for ( let i = 0; i < n; ++i ) {
    v = fn( i );
  }

  return v;
}

let mem = memoize( loop );

console.log( mem( Math.sqrt, 1e9 ) ); // slow
console.log( mem( Math.sqrt, 1e9 ) ); // fast!

Example with expire time in milliseconds

'use strict';

const memoize = require('@starryinternet/map-memo');

function getRandom() {
  return Math.random();
}

let mem = memoize( getRandom, { ttl: 1000 } );
console.log( mem() );
console.log( mem() ); // Same value as above

setTimeout( function() {
  console.log( mem() ); // Different value
}, 1001 );

Example with asynchronous function

'use strict';

const memoize = require('@starryinternet/map-memo');

function loopAsync( fn, n ) {
  return new Promise( ( resolve, reject ) => {
    let v;

    for ( let i = 0; i < n; ++i ) {
      v = fn( i );
    }

    resolve( v );
  });
}

let mem = memoize( loopAsync );

mem( Math.sqrt, 1e9 ).then( result => {
  console.log( result ); // slow
  mem( Math.sqrt, 1e9 ).then( console.log ); // fast!
});