107 lines
2.5 KiB
JavaScript
107 lines
2.5 KiB
JavaScript
/**
|
|
* @license Apache-2.0
|
|
*
|
|
* Copyright (c) 2018 The Stdlib Authors.
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
'use strict';
|
|
|
|
// MODULES //
|
|
|
|
var isFunction = require( '@stdlib/assert/is-function' );
|
|
var setReadOnly = require( './../../define-nonenumerable-read-only-property' );
|
|
var identity = require( './../../identity-function' );
|
|
var hasOwnProp = require( '@stdlib/assert/has-own-property' );
|
|
|
|
|
|
// MAIN //
|
|
|
|
/**
|
|
* Returns a memoized function.
|
|
*
|
|
* @param {Function} fcn - function to memoize
|
|
* @param {Function} [hashFunction] - function to map a set of arguments to a single value identifying that set
|
|
* @throws {TypeError} first argument must be a function
|
|
* @throws {TypeError} second argument must be a function
|
|
* @returns {Function} memoized function
|
|
*
|
|
* @example
|
|
* function factorial( n ) {
|
|
* var prod;
|
|
* var i;
|
|
* prod = 1;
|
|
* for ( i = n; i > 1; i-- ) {
|
|
* prod *= i;
|
|
* }
|
|
* return prod;
|
|
* }
|
|
*
|
|
* var memoized = memoize( factorial );
|
|
*
|
|
* var v = memoized( 5 );
|
|
* // returns 120
|
|
*
|
|
* v = memoized( 5 );
|
|
* // returns 120
|
|
*/
|
|
function memoize( fcn, hashFunction ) {
|
|
var toKey;
|
|
var cache;
|
|
if ( !isFunction( fcn ) ) {
|
|
throw new TypeError( 'invalid argument. First argument must be a function. Value: `'+fcn+'`.' );
|
|
}
|
|
if ( arguments.length < 2 ) {
|
|
toKey = identity;
|
|
} else {
|
|
toKey = hashFunction;
|
|
if ( !isFunction( toKey ) ) {
|
|
throw new TypeError( 'invalid argument. Hash function argument must be a function. Value: `' + toKey + '`.' );
|
|
}
|
|
}
|
|
cache = {};
|
|
setReadOnly( memoized, 'cache', cache );
|
|
return memoized;
|
|
|
|
/**
|
|
* Memoized function.
|
|
*
|
|
* @private
|
|
* @param {...*} args - function arguments
|
|
* @returns {*} memoized function result
|
|
*/
|
|
function memoized() {
|
|
var args;
|
|
var out;
|
|
var key;
|
|
var i;
|
|
args = new Array( arguments.length );
|
|
for ( i = 0; i < arguments.length; i++ ) {
|
|
args[ i ] = arguments[ i ];
|
|
}
|
|
key = toKey( args ).toString();
|
|
if ( hasOwnProp( cache, key ) ) {
|
|
return cache[ key ];
|
|
}
|
|
out = fcn.apply( null, args );
|
|
cache[ key ] = out;
|
|
return out;
|
|
}
|
|
}
|
|
|
|
|
|
// EXPORTS //
|
|
|
|
module.exports = memoize;
|