0.0.5 • Public • Published

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Observable store

An observable data store with dirty checking and computed properties.


npm install observable-store

How to use

Require observable-store:

var Store = require("observable-store");


It can be initialized with or without data. When initialized with data, a shallow clone is done first.

// Without data, an object based store:
var store = new Store({});
// Without data, an array base store:
var store = new Store([]);
// With an array
var store = new Store(["array", "of", "items"]);
// With an object
var store = new Store({
  property1: "object",
  property2: "with",
  property3: "data"

Standard CRUD methods

store.get(0); // "array";
store.get("property1"); // "object"
store.set(0, "new value"); // set or update the value
store.set("property1", "new value"); // set or update the value
store.del(0); // remove an item for the array
store.del("property1"); // remove the property from the array
// several items can be removed at once too
store.delAll(["property1", "property2"]);

Watch changes on specific property/item

The point of proxying accessing objects/arrays is that it can trigger events on what's changing. Examples of watching changes on specific properties or items:

var handle = store.watchValue("property1", function onPropertyUpdated(newValue, action, oldValue) {
  // newValue == "new value";
  // action == "updated"
  // oldValue == "object"
}, scope /* optional */);
store.set("property1", "new value");
var handle = store.watchValue(0, function onItemUpdated(newValue, action, oldValue) {
    // newValue is undefined
    // action == "deleted"
    // oldValue == "array"
}, scope /* optional */);
var handle = store.watchValue(3, function onItemUpdated(newValue, action, oldValue) {
    // newValue == "new value"
    // action == "added"
    // oldValue is undefined
}, scope /* optional */);
store.set(3, "new value");

Watch changes on generic events such as added/updated/deleted

You can also watch generic events on the whole array/object to know when a new item or property is added, updated or deleted. The following examples are for an object-based store but work the same way with arrays.

var handle = store.watch("added", function onPropertyAdded(propertyName, value) {
    // propertyName == "newProperty"
    // value == "new value"
}, scope /* optional */);
store.set("newProperty", "new value");
var handle = store.watch("updated", function onPropertyUpdated(propertyName, newValue, oldValue) {
    // propertyName == "newProperty"
    // newValue == "updated value"
    // oldValue == "new value"
}, scope /* optional */);
store.set("newProperty", "updated value");
var handle = store.watch("deleted", function onPropertyDeleted(propertyName, newValue, oldValue) {
    // propertyName == "newProperty"
    // newValue is undefined
    // oldValue == "updated value"

Unwatch changes

To unwatch, pass the handle to unwatch or unwatchValue

store.unwatch(handle); // for handles created by watch
store.unwatchValue(handle); // for handles created by watchValue

Using an array's native mutative methods

The data store has a method for accessing the array's native mutative methods to mutate the data store. When the changes have been made, the data store does a dirty check to figure out the changes and publish events accordingly. This example would also work with other methods than splice like pop, push, shift, unshift, sort, reverse.

// Let's remove item 0 and 1 from this store
var store = new Store([0, 1, 2, 3]);
store.watch("updated", function () {
    // this will be triggered two times:
    // The first item will be updated to 2
    // The second item will be updated to 3
store.watch("deleted", function () {
    // This will be triggered two times:
    // The first 3rd item will be deleted
    // The fourth item will be deleted
// For array-based stores
store.alter("splice", 0, 1); // returns [0, 1];

Using an array's accessor methods.

While alter would work in these cases too, using proxy instead doesn't trigger the dirty checking, so proxy is as fast as the native method itself. Other accessor methods are: concat, join, slice, toString, toLocalString, indexOf, lastIndexOf.

var store = new Store([0, 1, 2, 3]);
store.proxy("join", "|"); // returns "0|1|2|3";

Computed properties

The data store can also create computed properties out of other properties:

var store = new Store({
    "firstname": "John",
    "lastname": "Doe"
store.compute("name", ["firstname", "lastname"], function (firstname, lastname) {
    return this.get(firstname) + " " + this.get(lastname);
}, store /* optional */);
store.get("name"); // "John Doe"
store.isCompute("name"); // true

A computed property can also be watched upon:

// will be triggered if firstname or lastname changes
store.watchValue("name", function () { ... });
store.set("firstname", "Jim");

Store reset

The store can be reused and its data reset. When calling reset, the store will do a diff with the previous data and publish the relevant events.

// Will set the internal data and publish events for everything that has been changed/updated/added
store.reset({ ... });

Store utilities

store.toJSON(); // will serialize the data
store.dump(); // will return the internal structure
store.loop(function (value, key, object) {
    // do something with each value/key
    // object === store.dump();
}, scope /* optional */);


0.0.5 - 7 APR 2015

  • Update to watch-notify 0.0.3

0.0.4 - 5 APR 2015

  • Publish old value too when altering the store



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