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Deep Pluck
Extract a nested property value from each element of an object array.
Installation
npm install @stdlib/utils-deep-pluck
Usage
var deepPluck = require( '@stdlib/utils-deep-pluck' );
deepPluck( arr, path[, options] )
Extracts a nested property value from each element of an object array
based on a key path
.
var arr = [
{ 'a': { 'b': { 'c': 1 } } },
{ 'a': { 'b': { 'c': 2 } } }
];
var out = deepPluck( arr, 'a.b.c' );
// returns [ 1, 2 ]
A key path
may be specified as either a string
or as an array
.
var arr = [
{ 'a': [ 0, 1, 2 ] },
{ 'a': [ 3, 4, 5 ] }
];
var out = deepPluck( arr, [ 'a', 1 ] );
// returns [ 1, 4 ]
The function accepts the following options
:
-
copy:
boolean
indicating whether to return a new data structure. Default:true
. -
sep: key path separator. Default:
'.'
.
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
.
var arr = [
{ 'a': { 'b': { 'c': 1 } } },
{ 'a': { 'b': { 'c': 2 } } }
];
var out = deepPluck( arr, 'a.b.c', { 'copy': false } );
// returns [ 1, 2 ]
var bool = ( arr[ 0 ] === out[ 0 ] );
// returns true
The default key path
separator is .
. To specify an alternative separator, set the sep
option.
var arr = [
{ 'a': { 'b': { 'c': 1 } } },
{ 'a': { 'b': { 'c': 2 } } }
];
var out = deepPluck( arr, 'a|b|c', { 'sep': '|' } );
// returns [ 1, 2 ]
-
If a key path does not exist, the function sets the plucked value as
undefined
.var arr = [ { 'a': { 'b': { 'c': 1 } } }, null, void 0, { 'a': { 'b': { 'c': 2 } } } ]; var out = deepPluck( arr, 'a.b.c' ); // returns [ 1, undefined, undefined, 2 ]
-
Extracted values are not cloned.
var arr = [ { 'a': { 'b': { 'c': 2 } } }, { 'a': { 'b': { 'c': 3 } } } ]; var out = deepPluck( arr, 'a.b' ); // returns [ { 'c': 2 }, { 'c': 3 } ] var bool = ( arr[ 0 ].a.b === out[ 0 ] ); // returns true
To prevent subsequent unintended mutation, use copy.
var copy = require( '@stdlib/utils-copy' ); var arr = [ { 'a': { 'b': { 'c': 2 } } }, { 'a': { 'b': { 'c': 3 } } } ]; var out = deepPluck( arr, 'a.b' ); // returns [ { 'c': 2 }, { 'c': 3 } ] // Perform a deep copy: out = copy( out ); var bool = ( arr[ 0 ].a.b === out[ 0 ] ); // returns false
Examples
var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var deepPluck = require( '@stdlib/utils-deep-pluck' );
var arr;
var out;
var tmp;
var i;
arr = new Array( 100 );
for ( i = 0; i < arr.length; i++ ) {
tmp = {
'a': {
'b': {
'c': {
'd': null
}
}
}
};
tmp.a.b.c.d = round( randu()*100.0 );
arr[ i ] = tmp;
}
// Pluck the deeply nested values:
out = deepPluck( arr, 'a.b.c.d' );
console.log( out );
See Also
-
@stdlib/utils-deep-get
: get a nested property value. -
@stdlib/utils-deep-set
: set a nested property value.
Notice
This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
Community
License
See LICENSE.
Copyright
Copyright © 2016-2024. The Stdlib Authors.