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