wink-helpers

wink-helpers

Low level helper functions for Javascript arrays and objects used in wink

wink-helpers is a part of wink, which is a family of Machine Learning NPM packages. They consist of simple and/or higher order functions that can be combined with NodeJS stream and child processes to create recipes for analytics driven business solutions.

It offers a set of useful APIs to work on Javascript array and object. These APIs are used in most of the wink packages.

Installation

Use npm to install:

npm install wink-helpers --save

Usage

// Load wink helpers
var helpers = require( 'wink-helpers' );

console.log( helpers.array.isArray( [] ) );
// -> true

console.log( helpers.object.isObject( {} ) );
// -> true

console.log( helpers.object.isObject( new Set() ) )
// -> false

console.log( helpers.object.table( { mobile: 33, chargers: 45, usb: 27 } ) );
// -> [ [ "mobile", 33 ], [ "chargers", 45 ], [ "usb", 27 ] ]

var ppl = [ { name: 'john', age: 42 }, { name: 'marry', age: 37 } ];
console.log( ppl.sort( ascendingOn( 'age' ) ) );
// -> [ { "name": "marry", "age": 37 }, { "name": "john", "age": 42 } ]

console.log( helpers.array.product( [ [ 9, 8 ], [ 1, 2 ] ] ) );
// -> [ [ 9, 1 ], [ 9, 2 ], [ 8, 1 ], [ 8, 2 ] ]

API

The helper functions are classified into 2 categories viz. array and object.

array

isArray( value )

Tests if argument value is a valid JS array; returns true if it is, otherwise returns false.

sorting compare functions

It is a set of handy compare functions for handling a variety of array sorting needs.

compareFunction	Description
ascending	Sorts elements in an ascending order.
descending	Sorts elements in an descending order.
ascendingOnKey	It works on array of arrays, where each element is in the [ key, value ] format. Sorts elements in an ascending order on the key.
descendingOnKey	It works on array of arrays, where each element is in the [ key, value ] format. Sorts elements in an descending order on the key.
ascendingOnValue	It works on array of arrays, where each element is in the [ key, value ] format. Sorts elements in an ascending order on the value.
descendingOnValue	It works on array of arrays, where each element is in the [ key, value ] format. Sorts elements in an descending order on the value.
ascendingOn( accessor1 [,accessor2] )	A higher order function that returns a compare function for the accessors and can be directly used as the compare function for sort.It works on array of arrays or objects. Here the accessor specifies the key whose value will be used to determine the sort order. When both the accessors are supplied then the generated function sorts on a key composed of the two accessors and not on two different keys.
descendingOn( accessor1 [,accessor2] )	Same as above, but sorts in descending order.

pluck( array, key, limit )

Plucks the values specified by the key from each element of the array of arrays or objects, and returns the resultant array. The default value of key is 0. The number of elements to be plucked is defined by the limit, whose default value is array.length.

product( array )

Returns the cartesian product of the arrays present inside the array argument. For example, if the array argument is [ [ 1, 2, 3 ], [ 4 ], [ 5, 6 ] ], then the return value will be:

[
  [ 1, 4, 5 ],
  [ 1, 4, 6 ],
  [ 2, 4, 5 ],
  [ 2, 4, 6 ],
  [ 3, 4, 5 ],
  [ 3, 4, 6 ]
]

object

isObject( v )

Tests if argument v is a JS object; returns true if it is, otherwise returns false.

keys( obj )

Returns keys of the obj in an array.

size( obj )

Returns the number of keys in the obj.

value( obj )

Returns all the values from each key/value pair in the obj in form of an array.

valueFreq( obj )

Returns the frequency or count of every unique value from each key/value pair in the obj in form of an array.

table( obj [, f] )

Converts each key/value pair in the obj into an array of [ key, value ] pairs in form of a table (i.e. an array of array). Second argument - f is optional; it is a function, which is called with each value.

Need Help?

If you spot a bug and the same has not yet been reported, raise a new issue or consider fixing it and sending a pull request.

Copyright & License

wink-helpers is copyright 2017 GRAYPE Systems Private Limited.

It is licensed under the under the terms of the GNU Affero General Public License as published by the Free Software Foundation, version 3 of the License.