99 lines
2.1 KiB
Markdown
99 lines
2.1 KiB
Markdown
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@license Apache-2.0
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Copyright (c) 2019 The Stdlib Authors.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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# Non-Index Keys
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> Return an array of an object's own enumerable property names which are not integer indices.
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<section class="usage">
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## Usage
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```javascript
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var nonIndexKeys = require( '@stdlib/utils/nonindex-keys' );
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```
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#### nonIndexKeys( obj )
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Returns an `array` of an object's own enumerable property names which are not integer indices.
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```javascript
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var arr = [ 1, 2, 3 ];
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arr.a = 'foo';
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arr.b = 'bar';
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var keys = nonIndexKeys( arr );
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// e.g., returns [ 'a', 'b' ]
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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## Notes
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- Name order is not guaranteed, as `object` key enumeration is not specified according to the [ECMAScript specification][ecma-262-for-in]. In practice, however, most engines use insertion order to sort an `object`'s keys, thus allowing for deterministic extraction.
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- In contrast to the built-in `Object.keys()`, if provided `null` or `undefined`, the function returns an empty `array`, rather than throwing an error.
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</section>
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<!-- /.notes -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var nonIndexKeys = require( '@stdlib/utils/nonindex-keys' );
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function Foo() {
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this[ 0 ] = 3.14;
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this.beep = 'boop';
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this.a = {
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'b': 'c'
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};
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return this;
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}
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Foo.prototype.foo = [ 'bar' ];
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var obj = new Foo();
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var keys = nonIndexKeys( obj );
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console.log( keys );
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// e.g., => [ 'beep', 'a' ]
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```
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</section>
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<!-- /.examples -->
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<section class="links">
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[ecma-262-for-in]: http://www.ecma-international.org/ecma-262/5.1/#sec-12.6.4
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</section>
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<!-- /.links -->
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