time-to-botec

Benchmark sampling in different programming languages
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key_by.js (2144B)

      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 isCollection = require( '@stdlib/assert/is-collection' );
     24 var isFunction = require( '@stdlib/assert/is-function' );
     25 
     26 
     27 // MAIN //
     28 
     29 /**
     30 * Converts a collection to an object whose keys are determined by a provided function and whose values are the collection values.
     31 *
     32 * @param {Collection} collection - input collection
     33 * @param {Function} fcn - function to invoke
     34 * @param {*} [thisArg] - execution context
     35 * @throws {TypeError} first argument must be an object
     36 * @throws {TypeError} second argument must be a function
     37 * @returns {Object} output object
     38 *
     39 * @example
     40 * function toKey( value, index ) {
     41 *     console.log( '%d: %s', index, JSON.stringify( value ) );
     42 *     return value.name;
     43 * }
     44 *
     45 * var collection = [
     46 *     { 'name': 'beep', 'a': 1 },
     47 *     { 'name': 'boop', 'b': 2 }
     48 * ];
     49 *
     50 * var obj = keyBy( collection, toKey );
     51 * // returns { 'beep': { 'name': 'beep', 'a': 1 }, 'boop': { 'name': 'boop', 'b': 2 } }
     52 */
     53 function keyBy( collection, fcn, thisArg ) {
     54 	var out;
     55 	var len;
     56 	var key;
     57 	var i;
     58 	if ( !isCollection( collection ) ) {
     59 		throw new TypeError( 'invalid argument. First argument must be a collection. Value: `'+collection+'`.' );
     60 	}
     61 	if ( !isFunction( fcn ) ) {
     62 		throw new TypeError( 'invalid argument. Second argument must be a function. Value: `'+fcn+'`.' );
     63 	}
     64 	len = collection.length;
     65 	out = {};
     66 	for ( i = 0; i < len; i++ ) {
     67 		key = fcn.call( thisArg, collection[ i ], i );
     68 		out[ key ] = collection[ i ];
     69 	}
     70 	return out;
     71 }
     72 
     73 
     74 // EXPORTS //
     75 
     76 module.exports = keyBy;