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memoize
Memoize a function.
Installation
npm install @stdlib/utils-memoizeUsage
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 trueBy 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 15memoized.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
lengthof the returned function. Accordingly, the returned functionlengthis always0. - 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.
Community
License
See LICENSE.
Copyright
Copyright © 2016-2024. The Stdlib Authors.