134 lines
3.2 KiB
Markdown
134 lines
3.2 KiB
Markdown
<!--
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@license Apache-2.0
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Copyright (c) 2018 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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# mapValues
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> Map values from one object to a new object having the same keys.
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- Package usage documentation. -->
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<section class="usage">
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## Usage
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```javascript
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var mapValues = require( '@stdlib/utils/map-values' );
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```
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#### mapValues( obj, transform )
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Map values from one `object` to a new `object` having the same keys.
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```javascript
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function transform( value, key ) {
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return key + value;
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}
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var obj1 = {
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'a': 1,
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'b': 2
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};
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var obj2 = mapValues( obj1, transform );
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// returns { 'a': 'a1', 'b': 'b2' }
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```
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The `transform` function is provided three arguments:
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- `value`: object value corresponding to `key`
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- `key`: object key
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- `obj`: the input object
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</section>
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<!-- /.usage -->
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<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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## Notes
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- Key iteration 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 return values.
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- The function only maps values assigned to **own** properties. Hence, the function does **not** map values for inherited properties.
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- The function **shallow** copies key values.
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</section>
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<!-- /.notes -->
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<!-- Package usage examples. -->
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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 mapValues = require( '@stdlib/utils/map-values' );
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function transform( value, key ) {
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return key + ':' + value;
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}
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var obj1 = {
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'a': 'beep',
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'b': 'boop',
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'c': 'foo',
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'd': 'bar'
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};
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var obj2 = mapValues( obj1, transform );
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console.dir( obj2 );
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// => { 'a': 'a:beep', 'b': 'b:boop', 'c': 'c:foo', 'd': 'd:bar' }
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```
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</section>
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<!-- /.examples -->
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<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="references">
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</section>
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<!-- /.references -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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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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