113 lines
3.0 KiB
JavaScript
113 lines
3.0 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 isObject = require( '@stdlib/assert-is-object' );
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var isFunction = require( '@stdlib/assert-is-function' );
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var getPrototypeOf = require( '@stdlib/utils-get-prototype-of' );
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var hasOwnProp = require( '@stdlib/assert-has-own-property' );
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var nativeClass = require( '@stdlib/utils-native-class' );
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// VARIABLES //
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var objectPrototype = Object.prototype;
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// FUNCTIONS //
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/**
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* Tests that an object only has own properties.
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*
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* @private
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* @param {Object} obj - value to test
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* @returns {boolean} boolean indicating if an object only has own properties
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*/
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function ownProps( obj ) {
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var key;
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// NOTE: possibility of perf boost if key enumeration order is known (see http://stackoverflow.com/questions/18531624/isplainobject-thing).
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for ( key in obj ) {
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if ( !hasOwnProp( obj, key ) ) {
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return false;
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}
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}
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return true;
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}
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// MAIN //
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/**
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* Tests if a value is a plain object.
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*
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* @param {*} value - value to test
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* @returns {boolean} boolean indicating whether value is a plain object
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*
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* @example
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* var bool = isPlainObject( {} );
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* // returns true
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*
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* @example
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* var bool = isPlainObject( null );
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* // returns false
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*/
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function isPlainObject( value ) {
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var proto;
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// Screen for obvious non-objects...
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if ( !isObject( value ) ) {
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return false;
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}
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// Objects with no prototype (e.g., `Object.create( null )`) are plain...
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proto = getPrototypeOf( value );
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if ( !proto ) {
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return true;
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}
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// Objects having a prototype are plain if and only if they are constructed with a global `Object` function and the prototype points to the prototype of a plain object...
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return (
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// Cannot have own `constructor` property:
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!hasOwnProp( value, 'constructor' ) &&
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// Prototype `constructor` property must be a function (see also https://bugs.jquery.com/ticket/9897 and http://stackoverflow.com/questions/18531624/isplainobject-thing):
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hasOwnProp( proto, 'constructor' ) &&
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isFunction( proto.constructor ) &&
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nativeClass( proto.constructor ) === '[object Function]' &&
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// Test for object-specific method:
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hasOwnProp( proto, 'isPrototypeOf' ) &&
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isFunction( proto.isPrototypeOf ) &&
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(
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// Test if the prototype matches the global `Object` prototype (same realm):
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proto === objectPrototype ||
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// Test that all properties are own properties (cross-realm; *most* likely a plain object):
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ownProps( value )
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)
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);
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}
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// EXPORTS //
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module.exports = isPlainObject;
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