indexed-values

Related Blog Post.

Example

import {IndexedValues} from 'indexed-values';

// create a Set of unique values
const main = new IndexedValues;

// derive a set
const sub1 = main.bindValues(["a", "b", "c"]);
const sub2 = main.bindValues(["a"]);

// derived sets can make the main Set grow
if (!sub2.has("d"))
  sub2.add("d");

// {"main":["a","b","c","d"],"data":[[0,1,2],[0,3]]}
console.log(JSON.stringify({
  main,
  data: [sub1, sub2]
}));

API

The IndexedValues constructor extends the Set class, but it's a facade with the following peculiarities:

• it is not posible to delete a single value, or clear the instance. IndexedValues instances are ever-growing
• .toJSON() method returns an array of values held internally
• .valueOf() method returns a real Set that can resist postMessage, or be stored as IndexedDB
• .bindValues(values = []) returns a Set that can contain, add, or remove, any value. Added values will be reflected in the IndexedValues instance that created the bound Set.
• .bindIndexes(indexes = []) is like .bindValues() but uses indexes instead, to initialize the derived Set. This is mostly useful for revival.
• .mapKeys(entries = []) returns a Map where keys are derived from the IndexedValues. Added keys that are not known in the IndexedValues source, will be automatically added as part of the Set. Once serialized as JSON, these maps will represent all keys as indexes, because indeed these maps never hold keys as values, these hold keys as indexes.
• .mapEntries(entries = []) is the revival counter-part of .mapKeys(). It returns a map with keys revived from the IndexedValues instance.
• .fromIndexes(indexes) can revive right away Set instances, upgrading their prototype. This is a quick and dirty .bindIndexes() equivalent, available for performance reasons.
• .fromEntries(entries) can revive right away Map instances, upgrading their prototype. This is a quick and dirty .mapEntries() equivalent, available for performance reasons.