86 lines
2.6 KiB
JavaScript
86 lines
2.6 KiB
JavaScript
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var isCollection = require( '@stdlib/assert/is-collection' );
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var isFunction = require( '@stdlib/assert/is-function' );
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// MAIN //
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/**
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* Invokes a function once for each element in a collection and updates the collection in-place.
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*
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* ## Notes
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*
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* - The invoked function's return value is cached prior to updating a collection. Before updating the collection, a collection must be inspected to ensure that a collection has not been resized during invocation such that an index no longer has a corresponding element in the collection. Were a return value automatically used to update a collection, an input collection could be converted into a sparse data structure. While some might consider this a feature, here, we take stance that a user should be less clever.
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*
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*
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* @param {Collection} collection - input collection
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* @param {Function} fcn - function to invoke
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* @param {*} [thisArg] - execution context
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* @throws {TypeError} first argument must be a collection
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* @throws {TypeError} second argument must be a function
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* @returns {Collection} input collection
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*
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* @example
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* function scale( value, index, collection ) {
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* return value * index;
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* }
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*
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* var arr = [ 1, 2, 3, 4 ];
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*
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* var out = inmap( arr, scale );
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* // returns [ 0, 2, 6, 12 ]
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*
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* var bool = ( out === arr );
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* // returns true
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*/
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function inmap( collection, fcn, thisArg ) {
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var len;
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var v;
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var i;
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if ( !isCollection( collection ) ) {
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throw new TypeError( 'invalid argument. First argument must be a collection. Value: `'+collection+'`.' );
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}
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if ( !isFunction( fcn ) ) {
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throw new TypeError( 'invalid argument. Second argument must be a function. Value: `'+fcn+'`.' );
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}
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len = collection.length;
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for ( i = 0; i < len; i++ ) {
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v = fcn.call( thisArg, collection[ i ], i, collection );
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// Account for dynamically resizing a collection...
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if ( len !== collection.length ) {
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len = collection.length;
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}
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if ( i < len ) {
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collection[ i ] = v;
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}
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}
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return collection;
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}
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// EXPORTS //
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module.exports = inmap;
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