86 lines
2.5 KiB
JavaScript
86 lines
2.5 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 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 getOwnPropertyDescriptor = require( './../../property-descriptor' );
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var getPrototypeOf = require( './../../get-prototype-of' );
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// MAIN //
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/**
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* Returns a property descriptor for an object's inherited property.
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*
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* ## Notes
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*
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* - In contrast to the built-in `Object.getOwnPropertyDescriptor()`, this function returns `null` if provided `undefined` or `null`, rather than throwing an error.
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* - In contrast to the built-in `Object.getOwnPropertyDescriptor()`, this function returns `null` if an object does not have an inherited provided property, rather than `undefined`.
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*
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* @private
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* @param {*} value - input object
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* @param {(string|symbol)} property - property
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* @param {PositiveInteger} [level] - inheritance level
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* @throws {TypeError} third argument must be a positive integer
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* @returns {(Object|null)} property descriptor or null
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*
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* @example
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* var desc = inheritedPropertyDescriptor( {}, 'toString' );
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* // returns {...}
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*/
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function inheritedPropertyDescriptor( value, property, level ) { // eslint-disable-line id-length
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var desc;
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var obj;
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var N;
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var n;
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if ( arguments.length > 2 ) {
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if ( !isPositiveInteger( level ) ) {
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throw new TypeError( 'invalid argument. Third 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 null;
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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 in search of a specified property...
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n = 1;
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while ( obj && n <= N ) {
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desc = getOwnPropertyDescriptor( obj, property );
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if ( desc ) {
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return desc;
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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 null;
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}
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// EXPORTS //
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module.exports = inheritedPropertyDescriptor;
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