/** * @license Apache-2.0 * * Copyright (c) 2018 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. */ 'use strict'; // MODULES // var MAX_SAFE_INTEGER = require( '@stdlib/constants/float64/max-safe-integer' ); var isPositiveInteger = require( '@stdlib/assert/is-positive-integer' ).isPrimitive; var getOwnPropertyDescriptor = require( './../../property-descriptor' ); var getPrototypeOf = require( './../../get-prototype-of' ); // MAIN // /** * Returns a property descriptor for an object's inherited property. * * ## Notes * * - In contrast to the built-in `Object.getOwnPropertyDescriptor()`, this function returns `null` if provided `undefined` or `null`, rather than throwing an error. * - 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`. * * @private * @param {*} value - input object * @param {(string|symbol)} property - property * @param {PositiveInteger} [level] - inheritance level * @throws {TypeError} third argument must be a positive integer * @returns {(Object|null)} property descriptor or null * * @example * var desc = inheritedPropertyDescriptor( {}, 'toString' ); * // returns {...} */ function inheritedPropertyDescriptor( value, property, level ) { // eslint-disable-line id-length var desc; var obj; var N; var n; if ( arguments.length > 2 ) { if ( !isPositiveInteger( level ) ) { throw new TypeError( 'invalid argument. Third argument must be a positive integer. Value: `' + level + '`.' ); } N = level; } else { N = MAX_SAFE_INTEGER; } if ( value === null || value === void 0 ) { return null; } // Get the value's prototype: obj = getPrototypeOf( value ); // Walk the prototype chain in search of a specified property... n = 1; while ( obj && n <= N ) { desc = getOwnPropertyDescriptor( obj, property ); if ( desc ) { return desc; } obj = getPrototypeOf( obj ); n += 1; } return null; } // EXPORTS // module.exports = inheritedPropertyDescriptor;