map-helper v1.3.3

Map Helper

A Library for adding array-like functionality to Javascript Maps.

I love Javascript Maps, but they need some additional functionality to make them more useful. This library is an attempt to provide that functionality.

Install

install via npm

npm install --save map-helper

then in your application

import * as mapHelper from 'map-helper';

Methods

mapMap

takes and a Map and provides a new Map after applying a callback.

mapHelper.mapMap(map,callback)

Arguments

map (Map)

callback (function) Key, value, index

Returns

(Map)

Example

let foo = new Map([
    ["stuff",0],
    ["junk",1],
    ["gubbins",2]
]);

let bar = mapHelper.mapMap(foo, (key,value, index) => [key , value + 1]);

// result: Map(3) {"stuff" => 1, "junk" => 2, "gubbins" => 3}

reduceMap

Reduces a map based on a callback and an initial value.

mapHelper.mapMap(map,callback,inital)

Arguments

map (Map)

callback (function) Key, value, index

initial (any)

Returns

(any)

Example

let foo = new Map([
    ["stuff",0],
    ["junk",1],
    ["gubbins",2]
]);

let baz = mapHelper.reduceMap(foo, (current, key, value, index) => current + value , 0);

// result: 3

mergeMap

Merges an array of maps, aggregating key collisions as default behavior. Accepts an optional callback to handle collisions

mapHelper.mergeMap(maps,callback)

Arguments

maps (Array)

callback (function) Key, oldValue, newValue, numberOfCollisions

Returns

(Map)

Example

let foo = new Map([
    ["junk",1],
    ["gubbins",2]
]);

let anotherMap = new Map([
    ["mary", 1],
    ["gubbins", 4]
]);

let baz = mapHelper.reduceMap(foo, (current, key, value, index) => current + value , 0);

// result: Map(3) {"junk" => 1, "gubbins" => (2) [2, 4], "mary" => 1}

let mergedWithCallback = mapHelper.mergeMaps([foo, anotherMap], (key, oldVal, newVal, collisions) =>{
    return oldVal + newVal;
});

//result: Map(3) {"junk" => 1, "gubbins" => 6, "mary" => 1}

invertMap

Inverts the keys and values of a map, aggregating values with key collisions as default behaviour. accepts an options callback to handle key collisions.

mapHelper.invertMap(map,callback)

Arguments

map (Map)

callback (function) Key, oldValue, newValue, numberOfCollisions

Returns

(Map)

Example

let anotherMap = new Map([
    ["peter", 0],
    ["paul", 1],
    ["mary", 1],
    ["gubbins", 4]
]);

let invertedMap = mapHelper.invertMap(anotherMap);

// result: Map(3) {0 => "peter", 1 => (2) ["paul", "mary"], 4 => "gubbins"}

mapFromObject

converts a plain object to a map, using only own properties.

mapHelper.mapFromObject(object)

Arguments

object (Object)

Returns

(Map)

Example

let objectToConvert = {
    key1:"foo",
    key2:"bar",
    key3:"baz"
}

let convertedObject = mapHelper.mapFromObject(objectToConvert);

// result: Map(3) {"key1" => "foo", "key2" => "bar", "key3" => "baz"}