115 lines
3.6 KiB
JavaScript
115 lines
3.6 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 MAX_SAFE_INTEGER = require( '@stdlib/constants/float64/max-safe-integer' );
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var isPositiveInteger = require( '@stdlib/assert/is-positive-integer' ).isPrimitive;
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var getOwnPropertyDescriptors = require( './../../property-descriptors' );
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var getOwnPropertySymbols = require( './../../property-symbols' );
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var getPrototypeOf = require( './../../get-prototype-of' );
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var objectKeys = require( './../../keys' );
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var defineProperty = require( './../../define-property' );
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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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* Returns an object's inherited property descriptors.
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*
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* ## Notes
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*
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* - In contrast to the built-in `Object.getOwnPropertyDescriptors()`, this function returns an empty object if provided `undefined` or `null`, rather than throwing an error.
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*
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* @param {*} value - input object
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* @param {PositiveInteger} [level] - inheritance level
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* @throws {TypeError} second argument must be a positive integer
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* @returns {Object} inherited property descriptors
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*
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* @example
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* var desc = inheritedPropertyDescriptors( [] );
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* // returns {...}
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*/
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function inheritedPropertyDescriptors( value, level ) { // eslint-disable-line id-length
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var desc;
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var keys;
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var obj;
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var tmp;
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var N;
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var n;
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var i;
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if ( arguments.length > 1 ) {
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if ( !isPositiveInteger( level ) ) {
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throw new TypeError( 'invalid argument. Second argument must be a positive integer. Value: `' + level + '`.' );
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}
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N = level;
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} else {
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N = MAX_SAFE_INTEGER;
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}
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if ( value === null || value === void 0 ) {
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return {};
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}
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// Get the value's prototype:
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obj = getPrototypeOf( value );
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// Walk the prototype chain collecting all property descriptors...
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desc = {};
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n = 1;
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while ( obj && n <= N ) {
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tmp = getOwnPropertyDescriptors( obj );
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keys = objectKeys( tmp );
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for ( i = 0; i < keys.length; i++ ) {
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// The first encountered property descriptor for a property name always takes precedence...
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if ( !hasOwnProp( desc, keys[ i ] ) ) {
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// The following is equivalent to `desc[ keys[i] ] = {...}`, but accounts for the possibility of a "poisoned" `Object` prototype (i.e., an `Object.prototype` having a property with a setter which throws).
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defineProperty( desc, keys[ i ], {
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'configurable': true,
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'enumerable': true,
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'writable': true,
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'value': tmp[ keys[ i ] ]
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});
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}
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}
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keys = getOwnPropertySymbols( tmp );
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for ( i = 0; i < keys.length; i++ ) {
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// The first encountered property descriptor for a symbol property always takes precedence...
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if ( !hasOwnProp( desc, keys[ i ] ) ) {
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// The following is equivalent to `desc[ keys[i] ] = {...}`, but accounts for the possibility of a "poisoned" `Object` prototype (i.e., an `Object.prototype` having a property with a setter which throws).
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defineProperty( desc, keys[ i ], {
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'configurable': true,
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'enumerable': true,
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'writable': true,
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'value': tmp[ keys[ i ] ]
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});
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}
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}
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obj = getPrototypeOf( obj );
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n += 1;
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}
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return desc;
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}
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// EXPORTS //
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module.exports = inheritedPropertyDescriptors;
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