Map object extended with extra functional goodness.

Usage

Grab the package and add to your project

npm install --save better-map

Then add it to your code

const BetterMap = require ( ' better-map ' ) ;

API

Constructor

Takes an optional parameter of an iteratable object otherwise it returns an empty map.

const BetterMap = require ( ' better-map ' ) ; const expect = require ( ' code ' ) . expect ; const myMap = new BetterMap ( ) ; expect ( myMap . size ) . to . equal ( 0 ) ; const myOtherMap = new BetterMap ( [ [ ' one ' , 1 ] , [ ' two ' , 2 ] ] ) ; expect ( myOtherMap . size ) . to . equal ( 2 ) ;

entriesArray

Returns all of the entries as an array in the format of an array of arrays with key then value. Entries are returned in the order that they were added.

const BetterMap = require ( ' better-map ' ) ; const expect = require ( ' code ' ) . expect ; const test = new BetterMap ( [ [ ' one ' , 1 ] , [ ' two ' , 2 ] ] ) ; const actual = test . entriesArray ( ) ; expect ( actual ) . to . equal ( [ [ ' one ' , 1 ] , [ ' two ' , 2 ] ] ) ;

keysArray

Returns all of the keys as an array. Keys are returned in the order that the entries were added.

const BetterMap = require ( ' better-map ' ) ; const expect = require ( ' code ' ) . expect ; const test = new BetterMap ( [ [ ' one ' , 1 ] , [ ' two ' , 2 ] ] ) ; const actual = test . keysArray ( ) ; expect ( actual ) . to . equal ( [ ' one ' , ' two ' ] ) ;

filter

Takes a callback function and a thisArg parameter. It calls the callback function for every entry in the map with the parameter thisArg as the functions context (this) and returns all of the entries where the callback returned true as a new better-map.

The callback function takes value , key , map .

const BetterMap = require ( ' better-map ' ) ; const expect = require ( ' code ' ) . expect ; const test = new BetterMap ( [ [ ' one ' , 1 ] , [ ' two ' , 2 ] ] ) ; const actual = test . filter ( ( value , key ) => value === 2 ) ; expect ( actual ) . to . be . an . instanceOf ( BetterMap ) ; expect ( actual . size ) . to . equal ( 1 ) ; expect ( actual . has ( ' one ' ) ) . to . be . false ( ) ; expect ( actual . has ( ' two ' ) ) . to . be . true ( ) ;

map

Takes a callback function and a thisArg parameter. It calls the callback function for every entry in the map with the parameter thisArg as the functions context (this) and returns an array of the results of each call.

The callback function takes value , key , map . The value of the array entry will be the value returned from the callback.

const BetterMap = require ( ' better-map ' ) ; const expect = require ( ' code ' ) . expect ; const test = new BetterMap ( [ [ ' one ' , 1 ] , [ ' two ' , 2 ] ] ) ; const actual = test . map ( ( value , key ) => ` ${ key } = ${ value } ` ) ; expect ( actual ) . to . equal ( [ ' one = 1 ' , ' two = 2 ' ] ) ;

reduce

Takes a callback function and an initialValue parameter. It calls the callback function for every entry in the map and returns a single reduced value.

The callback function takes previousValue , value , key , map . The value of the array entry will be the value returned from the callback. previousValue will be undefined if an initialValue is not given.

const BetterMap = require ( ' better-map ' ) ; const expect = require ( ' code ' ) . expect ; const test = new BetterMap ( [ [ ' one ' , 1 ] , [ ' two ' , 2 ] ] ) ; const actual = test . reduce ( ( pv , cv ) => pv + cv , 0 ) ; expect ( actual ) . to . equal ( 3 ) ;

some

Takes a callback function and a thisArg parameter. It calls the callback function for every entry in the map with the parameter thisArg as the functions context (this). Returns a boolean .

The callback function takes value , key , map and must return a boolean value. A value of true signifies that a match has been made and will cause the loop to end straight away.

const BetterMap = require ( ' better-map ' ) ; const expect = require ( ' code ' ) . expect ; const test = new BetterMap ( [ [ ' one ' , 1 ] , [ ' two ' , 2 ] ] ) ; expect ( test . some ( ( value ) => value === 1 ) ) . to . equal ( true ) ; expect ( test . some ( ( value , key ) => key === ' three ' ) ) . to . equal ( false ) ;

stringify

JSON encode the instance. Will also encode child Map and Set objects.

const BetterMap = require ( ' better-map ' ) ; const expect = require ( ' code ' ) . expect ; const testMap = new BetterMap ( ) . set ( ' one ' , 1 ) . set ( ' two ' , ' a ' ) . set ( ' three ' , null ) . set ( ' a ' , [ 1 , 2 , 3 ] ) ; const expected = JSON . stringify ( { one : 1 , two : ' a ' , three : null , a : [ 1 , 2 , 3 ] } ) ; const actual = testMap . stringify ( ) ; expect ( actual ) . to . equal ( expected ) ;

toObject

Shallowly maps the current object to a object. Asserts that all of the keys for the map are strings.

const BetterMap = require ( ' better-map ' ) ; const expect = require ( ' code ' ) . expect ; const test = new BetterMap ( ) . set ( ' one ' , 1 ) . set ( ' two ' , ' a ' ) . set ( ' three ' , null ) ; expect ( test . toObject ( ) ) . to . equal ( { one : 1 , two : ' a ' , three : null } ) ;

valuesArray

Returns all of the values as an array. Values are returned in the order that the entries were added.