versioned-value-map v1.1.0

VersionedValueMap

The immutable, portable, serializable, restorable and extensible container of time-series data. You can add/remove values and new instance will be created. Easy integration with Redux and Phenyl.

Installation

$ npm install versioned-value-map

Basic usage

Importing

import { VersionedValueMap } from "versioned-value-map";

Add values

const map = new VersionedValueMap();
const newMap = map.$add("propName01", "foobar");

map is unchanged. newMap forms the following structure.

{
  items: {
    propName01: {
      name: 'propName01',
      records: [
        { value: 'foobar', at: '2018-03-02T18:56:00.222Z' },
      ],
    },
    bar: {
      ...
    }
  }
}

You can see that the timestamp is automatically added into the records.

Add value with timestamp

The 3rd argument is reserved for timestamp.

const newMap = map.$add("propName01", "foobar", "2018-03-02T18:56:00.222Z");

Get values

Current values

Just call map.get(name).

const map = new VersionedValueMap().$add("propName01", "foobar");
const currentValue = map.get("propName01");
assert(currentValue === "foobar");

Trying to non-registered value will get null.

const currentValue = map.get("abc");
assert(currentValue == null);

Get Item

const item = map.getItem("propName01");

item is the instance of VersionedValue and forms the following structure.

{
  name: 'propName01',
  records: [
    { value: 'foobar', at: '2018-03-02T18:56:00.222Z' }
  ]
}

These all properties are public and feel free to access to them like the following.

const createdAt = map.getItem("propName01").records[0].at;

Remove values

Removing the newest value:

const newMap = map.$removeNewest("propName01");

Make sure map is unchanged.

Remove the specific value with timestamp

You can use map.$remove(name, at) here.

const newMap = map.$remove("propName01", "2018-03-02T18:56:00.222Z");

Serialization

VersionedValueMap is Restorable. That means it can be re-created by passing its JSON object to the class constructor.

In the following case, map is deeply equal to newMap.

const plainMap = JSON.parse(JSON.stringify(map));
const newMap = new VersionedValueMap(plainMap);

The plain map's structure is as follows.

{
  items: {
    foo: {
      name: 'foo',
      records: [
        { value: 1, at: '2018-03-02T18:56:00.222Z' },
        { value: 7, at: '2018-03-04T03:11:23.524Z' },
      ],
    },
    bar: {
      ...
    }
  }
}

Integration with Redux

Understanding UpdateOperation

const map = new VersionedValueMap();
const operation = map.add("propName01", "foobar");

Unlike $add() which directly create new map, add() create UpdateOperation instead. operation here contains the operation to update map as data.

{
  $set: {
    'items.propName01': { name: 'propName01', records: [{ value: 'foobar', at: '2018-03-02T18:56:00.222Z' }] }
  }
}

This format is almost the same as MongoDB's Update Operators. See power-assign Documentation for more detailed information.

power-assign

UpdateOperation can be parsed by a simple library called power-assign. Pass the operation above to assign() to create a new object.

import { assign } from "@sp2/updater";

const newPlainMap = assign(oldMap, operation); // NewMap = OldMap + UpdateOperation

const newMap = new VersionedValueMap(newPlainMap);

As assign() returns plain object, you must call constructor after that.

Alternatively, updateAndRestore() automatically do this.

import { updateAndRestore } from "@sp2/updater";

const newMap = updateAndRestore(oldMap, operation);

Writing these code in Reducer function, you can handle the state of VersionedValueMap with Redux.

example

First, let's define the reducer.

import { assignToProp } from 'power-assign'

function reducer(state, action) {
  if (!state) {
    return { map: {} } // expect plain VersionedValueMap
  }
  if (action.type === 'update-map') {
    const updateOperation = action.payload
    // This immutably assigns the update operation to "map"
    return assignToProp(state, 'map', updateOperation)
  }
  ...
}

assignToProp() is like assign() but it assigns not to the state but to state.map.

Action will be dispatched like this:

const state = store.getState();
const map = new VersionedValueMap(state.map);
const updateOperation = map.add("propName01", "foobar");
const action = {
  type: "update-map",
  payload: updateOperation
};
dispatch(action);

Make sure that state contains plain map object and every time reducer is called the map is constructed by new VersionedValueMap(state.map). We've benchmarked the performance and found that a map with 5000 items containing 10 datapoints will be constructed within 1msec (in Node.js v8). That means that we can ignore the construction cost in modern JS environments.

Flow

If you are using flow, you can use its type by the following statement.

import { VersionedValueMap } from "versioned-value-map/jsnext";

This jsnext.js exports pre-transpiled sources, which is helpful in developing phase. In transpiling/bundling phase, however, maybe you want this package to be transpiled. In this case, it would be helpful to use a babel-plugin called babel-plugin-transform-strip-jsnext to strip the /jsnext suffix.

npm install babel-plugin-transform-strip-jsnext

.babelrc

{
  "plugins": ["transform-strip-jsnext"]
}

Also make sure to add the following line to the [options] section in your .flowconfig.

suppress_comment=.*\\$FlowIssue(\\(.*\\))?

Put type map for better inference

Put type map in initializing instances as below.

import { VersionedValueMap } from "versioned-value-map/jsnext";

const map: VersionedValueMap<{
  foo: string,
  bar: number
}> = new VersionedValueMap();

Then, flow can get its types.

const str = map.get("foo");
if (str != null) {
  // here, str is regarded as string
}

const num = map.get("bar");
if (num != null) {
  // here, num is regarded as number
}

API Documentation

TBD

LICENSE

Apache License 2.0