48 lines
1.3 KiB
JavaScript
48 lines
1.3 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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/**
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* Tests if a value is `undefined`.
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*
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* ## Notes
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*
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* - In older browsers, `undefined` is a global which can be overridden. `void`, however, is an operator which **cannot** be overridden. Consequently, better to use `void` to check for `undefined`. See [Stack Overflow][1].
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*
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* [1]: http://stackoverflow.com/a/19369078/2225624
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*
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* @param {*} value - value to test
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* @returns {boolean} boolean indicating whether value is undefined
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*
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* @example
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* var bool = isUndefined( undefined );
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* // returns true
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*
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* bool = isUndefined( null );
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* // returns false
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*/
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function isUndefined( value ) {
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return value === void 0;
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}
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// EXPORTS //
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module.exports = isUndefined;
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