time-to-botec

Benchmark sampling in different programming languages
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memoize.js (2603B)

      1 /**
      2 * @license Apache-2.0
      3 *
      4 * Copyright (c) 2018 The Stdlib Authors.
      5 *
      6 * Licensed under the Apache License, Version 2.0 (the "License");
      7 * you may not use this file except in compliance with the License.
      8 * You may obtain a copy of the License at
      9 *
     10 *    http://www.apache.org/licenses/LICENSE-2.0
     11 *
     12 * Unless required by applicable law or agreed to in writing, software
     13 * distributed under the License is distributed on an "AS IS" BASIS,
     14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     15 * See the License for the specific language governing permissions and
     16 * limitations under the License.
     17 */
     18 
     19 'use strict';
     20 
     21 // MODULES //
     22 
     23 var isFunction = require( '@stdlib/assert/is-function' );
     24 var setReadOnly = require( './../../define-nonenumerable-read-only-property' );
     25 var identity = require( './../../identity-function' );
     26 var hasOwnProp = require( '@stdlib/assert/has-own-property' );
     27 
     28 
     29 // MAIN //
     30 
     31 /**
     32 * Returns a memoized function.
     33 *
     34 * @param {Function} fcn - function to memoize
     35 * @param {Function} [hashFunction] - function to map a set of arguments to a single value identifying that set
     36 * @throws {TypeError} first argument must be a function
     37 * @throws {TypeError} second argument must be a function
     38 * @returns {Function} memoized function
     39 *
     40 * @example
     41 * function factorial( n ) {
     42 *     var prod;
     43 *     var i;
     44 *     prod = 1;
     45 *     for ( i = n; i > 1; i-- ) {
     46 *         prod *= i;
     47 *     }
     48 *     return prod;
     49 * }
     50 *
     51 * var memoized = memoize( factorial );
     52 *
     53 * var v = memoized( 5 );
     54 * // returns 120
     55 *
     56 * v = memoized( 5 );
     57 * // returns 120
     58 */
     59 function memoize( fcn, hashFunction ) {
     60 	var toKey;
     61 	var cache;
     62 	if ( !isFunction( fcn ) ) {
     63 		throw new TypeError( 'invalid argument. First argument must be a function. Value: `'+fcn+'`.' );
     64 	}
     65 	if ( arguments.length < 2 ) {
     66 		toKey = identity;
     67 	} else {
     68 		toKey = hashFunction;
     69 		if ( !isFunction( toKey ) ) {
     70 			throw new TypeError( 'invalid argument. Hash function argument must be a function. Value: `' + toKey + '`.' );
     71 		}
     72 	}
     73 	cache = {};
     74 	setReadOnly( memoized, 'cache', cache );
     75 	return memoized;
     76 
     77 	/**
     78 	* Memoized function.
     79 	*
     80 	* @private
     81 	* @param {...*} args - function arguments
     82 	* @returns {*} memoized function result
     83 	*/
     84 	function memoized() {
     85 		var args;
     86 		var out;
     87 		var key;
     88 		var i;
     89 		args = new Array( arguments.length );
     90 		for ( i = 0; i < arguments.length; i++ ) {
     91 			args[ i ] = arguments[ i ];
     92 		}
     93 		key = toKey( args ).toString();
     94 		if ( hasOwnProp( cache, key ) ) {
     95 			return cache[ key ];
     96 		}
     97 		out = fcn.apply( null, args );
     98 		cache[ key ] = out;
     99 		return out;
    100 	}
    101 }
    102 
    103 
    104 // EXPORTS //
    105 
    106 module.exports = memoize;