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* @license Apache-2.0
*
* Copyright (c) 2025 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.
*/
/* eslint-disable no-invalid-this */
'use strict';
// MODULES //
var setNonEnumerableReadOnly = require( '@stdlib/utils/define-nonenumerable-read-only-property' );
var setReadWriteAccessor = require( '@stdlib/utils/define-read-write-accessor' );
var resolveGetter = require( '@stdlib/array/base/resolve-getter' );
var objectKeys = require( '@stdlib/utils/keys' );
// MAIN //
/**
* Returns an array containing views with renamed keys for every element in a provided array.
*
* ## Notes
*
* - The function returns views having only those keys which are present in a provided mapping object. Any keys which are not present in the provided mapping object, but are present in the original objects, are omitted during view creation.
* - The function assumes that each object has the keys specified in a provided mapping object.
* - Each view in the returned array shares the same memory as the corresponding elements in the input arrays. Accordingly, mutation of either an array element or a view will mutate the other.
*
* @param {ArrayLikeObject<Object>} arr - input array
* @param {Object} mapping - object mapping existing keys to new key names
* @returns {Array<Object>} output array
*
* @example
* var x = [
* {
* 'x': 1,
* 'y': 2
* },
* {
* 'x': 3,
* 'y': 4
* }
* ];
* var mapping = {
* 'x': 'a',
* 'y': 'b'
* };
*
* var out = rekeyViews( x, mapping );
* // returns [ <Object>, <Object> ]
*
* var v0 = out[ 0 ].toJSON();
* // returns { 'a': 1, 'b': 2 }
*
* var v1 = out[ 1 ].toJSON();
* // returns { 'a': 3, 'b': 4 }
*
* // Mutate the first element in the input array:
* x[ 0 ].x = 5;
*
* v0 = out[ 0 ].toJSON();
* // returns { 'a': 5, 'b': 2 }
*
* // Set a view property:
* out[ 1 ].b = 'beep';
*
* v1 = out[ 1 ].toJSON();
* // returns { 'a': 3, 'b': 'beep' }
*
* var y = x.slice();
* // returns [ { 'x': 5, 'y': 2 }, { 'x': 3, 'y': 'beep' } ]
*/
function rekeyViews( arr, mapping ) {
var getter;
var okeys;
var nkeys;
var out;
var M;
var N;
var i;
M = arr.length;
if ( M < 1 ) {
return [];
}
// Resolve the list of old key names:
okeys = objectKeys( mapping );
N = okeys.length;
// Resolve the list of new key names:
nkeys = [];
for ( i = 0; i < N; i++ ) {
nkeys.push( mapping[ okeys[ i ] ] );
}
// Resolve the accessor for the input array:
getter = resolveGetter( arr );
// eslint-disable-next-line stdlib/jsdoc-typedef-typos
/**
* Constructor for creating a composite view.
*
* @private
* @constructor
* @param {NonNegativeInteger} i - element index
* @returns {Datum} datum instance
*/
function Datum( i ) {
setNonEnumerableReadOnly( this, '_i', i );
return this;
}
// Define accessors for each field...
for ( i = 0; i < N; i++ ) {
setReadWriteAccessor( Datum.prototype, nkeys[ i ], getValue( okeys[ i ] ), setValue( okeys[ i ] ) ); // eslint-disable-line max-len
}
// Ensure that the returned array correctly serializes to JSON:
setNonEnumerableReadOnly( Datum.prototype, 'toJSON', toJSON );
// Create a list of composite views...
out = [];
for ( i = 0; i < M; i++ ) {
out.push( new Datum( i ) );
}
return out;
/**
* Returns an accessor for returning the value associated with a field.
*
* @private
* @param {string} key - field name
* @returns {Function} accessor
*/
function getValue( key ) {
return get;
/**
* Returns the value associated with a field.
*
* @private
* @returns {*} result
*/
function get() {
return getter( arr, this._i )[ key ];
}
}
/**
* Returns an accessor for setting the value associated with a field.
*
* @private
* @param {string} key - field name
* @returns {Function} accessor
*/
function setValue( key ) {
return set;
/**
* Sets the value associated with a field.
*
* @private
* @param {*} value - value to set
*/
function set( value ) {
getter( arr, this._i )[ key ] = value;
}
}
/**
* Serializes a datum to JSON.
*
* @private
* @returns {Object} JSON object
*/
function toJSON() {
var out;
var k;
var i;
out = {};
for ( i = 0; i < N; i++ ) {
k = nkeys[ i ];
out[ k ] = this[ k ];
}
return out;
}
}
// EXPORTS //
module.exports = rekeyViews;
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