82 lines
2.2 KiB
JavaScript
82 lines
2.2 KiB
JavaScript
/**
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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 isFunction = require( '@stdlib/assert/is-function' );
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var hasOwnProp = require( '@stdlib/assert/has-own-property' );
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// MAIN //
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/**
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* Maps keys from one object to a new object having the same values.
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*
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* ## Notes
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*
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* - Iteration order is **not** guaranteed.
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* - We need to cache an object value to prevent the edge case where, during the invocation of the transform function, the value corresponding to a particular key is swapped for some other value. For some, that might be a feature; here, we take the stance that one should be less clever.
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*
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*
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* @param {Object} obj - source object
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* @param {Function} transform - transform function
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* @throws {TypeError} first argument must be an object
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* @throws {TypeError} second argument must be a function
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* @returns {Object} new object
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*
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* @example
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* function transform( key, value ) {
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* return key + value;
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* }
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*
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* var obj1 = {
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* 'a': 1,
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* 'b': 2
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* };
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*
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* var obj2 = mapKeys( obj1, transform );
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* // returns { 'a1': 1, 'b2': 2 }
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*/
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function mapKeys( obj, transform ) {
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var out;
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var key;
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var v;
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if ( typeof obj !== 'object' || obj === null ) {
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throw new TypeError( 'invalid argument. First argument must be an object. Value: `'+obj+'`.' );
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}
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if ( !isFunction( transform ) ) {
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throw new TypeError( 'invalid argument. Second argument must be a function. Value: `'+transform+'`.' );
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}
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out = {};
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for ( key in obj ) {
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if ( hasOwnProp( obj, key ) ) {
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v = obj[ key ];
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key = transform( key, v, obj );
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out[ key ] = v;
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}
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}
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return out;
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}
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// EXPORTS //
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module.exports = mapKeys;
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