@stdlib/utils-memoize NPM

memoize

Memoize a function.

Installation

npm install @stdlib/utils-memoize

Usage

var memoize = require( '@stdlib/utils-memoize' );

memoize( fcn[, hashFunction] )

Memoizes a function.

var randu = require( '@stdlib/random-base-randu' );

function rand( n ) {
    return n * randu();
}

var memoized = memoize( rand );

var v1 = memoized( 5 );
var v2 = memoized( 5 );

var bool = ( v1 === v2 );
// returns true

By default, the implementation serializes provided arguments as a string and stores results using the string as an identifier. To use a custom hash function, provide a hash function argument.

function add( obj ) {
    return obj.x + obj.y + obj.z;
}

obj = {
    'x': 3,
    'y': 4,
    'z': 5
};

// Default behavior...

var memoized = memoize( add );

var v1 = memoized( obj );
// returns 12

var str = obj.toString();
// returns '[object Object]'

var v2 = memoized.cache[ str ];
// returns 12

obj.x = 1000;

var v3 = memoized( obj );
// returns 12

// Custom hash function...

function hashFunction( args ) {
    return JSON.stringify( args );
}

memoized = memoize( add, hashFunction );

v1 = memoized( obj );
// returns 1009

str = hashFunction( [ obj ] );
// returns '[{"x":1000,"y":4,"z":5}]'

v2 = memoized.cache[ str ];
// returns 1009

obj.x = 6;

v3 = memoized( obj );
// returns 15

memoized.cache

Results cache. Note that, while the property is read-only, cache contents may be modified independently of the memoized function.

function beep( x ) {
    throw new Error( 'boop' );
}

var memoized = memoize( beep );

var cache = memoized.cache;
// returns {}

// Modify the cache:
cache[ 'bop' ] = 'bip';

var str = memoized( 'bop' );
// returns 'bip'

Notes

The implementation does not set the length of the returned function. Accordingly, the returned function length is always 0.
The evaluation context is always null.

Examples

var randu = require( '@stdlib/random-base-randu' );
var floor = require( '@stdlib/math-base-special-floor' );
var memoize = require( '@stdlib/utils-memoize' );

var fcn;
var n;
var v;
var i;

function rand( n ) {
    return n * randu();
}

fcn = memoize( rand );

for ( i = 0; i < 100; i++ ) {
    n = floor( randu() * 5 );
    v = fcn( n );
    console.log( 'rand(%d) = %d', n, v );
}

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.