time-to-botec/js/node_modules/@stdlib/utils/pluck/README.md

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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
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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limitations under the License.
-->
# Pluck
> Extract a property value from each element of an object array.
<section class="intro">
</section>
<!-- /.intro -->
<section class="usage">
## Usage
```javascript
var pluck = require( '@stdlib/utils/pluck' );
```
#### pluck( arr, prop\[, options] )
Extracts a property value from each element of an object `array`.
<!-- eslint-disable object-curly-newline, object-property-newline -->
```javascript
var arr = [
{ 'a': 1, 'b': 2 },
{ 'a': 0.5, 'b': 3 }
];
var out = pluck( arr, 'a' );
// returns [ 1, 0.5 ]
```
The function accepts the following `options`:
- **copy**: `boolean` indicating whether to return a new data structure. Default: `true`.
By default, the function returns a new data structure. To mutate the input data structure (e.g., when input values can be discarded or when optimizing memory usage), set the `copy` option to `false`.
<!-- eslint-disable object-curly-newline, object-property-newline -->
```javascript
var arr = [
{ 'a': 1, 'b': 2 },
{ 'a': 0.5, 'b': 3 }
];
var out = pluck( arr, 'a', { 'copy': false } );
// returns [ 1, 0.5 ]
var bool = ( arr[ 0 ] === out[ 0 ] );
// returns true
```
</section>
<!-- /.usage -->
<section class="notes">
## Notes
- The function skips `null` and `undefined` array elements.
<!-- eslint-disable object-curly-newline, object-property-newline -->
```javascript
var arr = [
{ 'a': 1, 'b': 2 },
null,
void 0,
{ 'a': 0.5, 'b': 3 }
];
var out = pluck( arr, 'a' );
// returns [ 1, , , 0.5 ]
```
- Extracted values are **not** cloned.
<!-- eslint-disable object-curly-newline, object-curly-spacing -->
```javascript
var arr = [
{ 'a': { 'b': 2 } },
{ 'a': { 'b': 3 } }
];
var out = pluck( arr, 'a' );
// returns [ { 'b': 2 }, { 'b': 3 } ]
var bool = ( arr[ 0 ].a === out[ 0 ] );
// returns true
```
To prevent unintended mutation, use [copy][@stdlib/utils/copy].
<!-- eslint-disable object-curly-newline, object-curly-spacing -->
```javascript
var copy = require( '@stdlib/utils/copy' );
var arr = [
{ 'a': { 'b': 2 } },
{ 'a': { 'b': 3 } }
];
var out = pluck( arr, 'a' );
// returns [ { 'b': 2 }, { 'b': 3 } ]
// Perform a deep copy:
out = copy( out );
var bool = ( arr[ 0 ].a === out[ 0 ] );
// returns false
```
</section>
<!-- /.notes -->
<section class="examples">
## Examples
<!-- eslint no-undef: "error" -->
```javascript
var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var pluck = require( '@stdlib/utils/pluck' );
var arr;
var tmp;
var out;
var i;
var j;
// Generate a 100x5 2d-array...
arr = new Array( 100 );
for ( i = 0; i < arr.length; i++ ) {
tmp = new Array( 5 );
for ( j = 0; j < tmp.length; j++ ) {
tmp[ j ] = round( randu()*100.0*(j+1.0) );
}
arr[ i ] = tmp;
}
// Pluck the 3rd column:
out = pluck( arr, 2 );
console.log( out );
```
</section>
<!-- /.examples -->
<section class="links">
[@stdlib/utils/copy]: https://www.npmjs.com/package/@stdlib/utils/tree/main/copy
</section>
<!-- /.links -->