SuperMap

SuperMap is a zero dependency ADT like JS MAP but with super powers 😎, is implemented with Typescript so it's completely typed.

This package is 100% compatible with the Map structure built in the language by default, indeed the original one is used under the hood and the new features are implemented using Monkey Patching.

Installation

npm install @omenlog/super-map

SuperMap is a factory function so for create a new super map we call the function without use the new operator, besides that we can pass an array of key value pairs during the initialization in the same way like the JS Map.

import { SuperMap } from '@omenlog/super-map';

const map = SuperMap(); // empty superMap

const mapWithValues = SuperMap([["key", 1]]); // superMap with one entry 

Fallback values on get

get method support a second argument that is used as fallback if the key accessed is undefined,in that case the fallback value is assigned to the current key and returned.

const map = SuperMap<string, number>();
const defaultValue = 10;

console.log(map.get("key", defaultValue))); // 10
console.log(map.get("key")); // 10

console.log(map.get("not-defined-key"));  // undefined

Update values

SuperMap has an update method that allow update values very easily

const map = SuperMap<string, number>();

map.set("key", 1);

map.update("key", 2);

console.log(map.get("key")); // 2 value update

Also if we want to apply the update operation based on the existing value, a function can be passed as second argument, in that case the updater function will be called with the previous value to produce a new one.

const map = SuperMap<string, number>();

map.set("key", 1);

map.update("key", v => v + 10);

console.log(map.get("key")); // 11

//value update from the previous one

map

Every super map is a functor then is possible apply a mapper function over every one of its values to obtain a new super map after the transformation.

const sm = SuperMap([["key", 1], ["another-key", 2]]);

const newMap = sm.map(v => v * 2);

console.log(newMap.get("key")); // 2
console.log(newMap.get("another-key")); // 4

The mapper function receive 3 arguments the value its key and the supermap being transformed, one details about this function is that it shouldn't return null or undefined, in that case we will have a type error.

filter

We can filter super map values based on some predicate to obtain a new map.

const map = SuperMap([["one-key", 1], ["two-key", 2]]);

const newSuperMap = map.filter(v => v % 2 === 0);

console.log(newSuperMap.size); // 1

console.log(newSuperMap.get("one-key")); // undefined

console.log(newSuperMap.get("two-key")); // 2

The function passed to filter must return a boolean and it receive the same 3 argumentslike the map method.

reduce

Every super map implement the reducer protocol, so they can be reduced very similar to how we can do it with JS Arrays

const map = SuperMap([["one-key", 1], ["two-key", 2]]);

const sum = map.reduce((acc,value) => acc + value); // is possible  pass an initial value as second argument

console.log(sum); // 3

reduceAsync

Sometimes we want to reduce our map applying some kind of async function, SuperMap support that use case through reduceAsync function. This function require that our reducer return a Promise, after the reduction is done we obtain a Promise with the final value.

const map = SuperMap([["key", 1], ["another-key", 2]]);

const asyncAverage = await map.reduceAsync((acc, val) => {
    return new Promise((resolve) => setTimeout(() => resolve(acc + val), 0));
}, 0);

console.log(asyncAverage) // 3;