stateZx

stateZ (state-easy) indeXedDB edition is a simple client-side state manager. Features:

• simple to use, e.g. myState.x = 1; console.log( myState.x );
• triggers events when a state changes
• synchronizes data across browser tabs and windows on the same domain
• vanilla JavaScript compatible with all frameworks
• also provides PixDB - a Promise-based indexedDB wrapper
• fast and lightweight - less than 4.5KB of code

Compatibility

stateZx works in modern browsers which support ES modules.

stateZ comparison

stateZx works in a different way to stateZ:

feature	stateZ	stateZx
code size	2Kb	4.5Kb
storage	session/localStorage	indexedDB
storage limit	typically 5MB	typically 1GB
data types	stringified values	values, objects, blobs
data lifetime	permanent, session, page	permanent
initial values	whole database or whole object only	individual properties
event triggering	change to store	change to store or an individual property
syncing	manual or on page unload	automatic, real-time
performance	good, but synchronous storage	good with asynchronous storage

stateZ is a good option for web sites with minimal storage requirements. stateZx may be preferable for complex web apps storing large amounts of data.

Installation

Load the module from a CDN:

import { stateZx } from 'https://cdn.jsdelivr.net/npm/statezx/dist/statezx.js';

If using npm and a bundler, install with:

npm install statezx

then import the module locally (path resolution will depend on the bundler):

import { stateZx } from './node_modules/statezx/dist/statezx.js';

Note that PixDB - a Promise-based indexedDB wrapper - is also available should you require it:

import { stateZx, PixDB } from ...

Examples

Create/access a named state store by passing an optional name and initialization object:

const state = await stateZx('myState', { a: 1, b: 2, c: 3 });

This returns a Promise so await is used. Any state object on any page which accesses the same myState store has access to the same properties. Values from the database initialize the properties. If a is not defined, the initialization object sets state.a to 1.

Set and retrieve values:

// set state
state.x = 123;
state.y = 'abc';

// get state
console.log( state.x, state.y ); // 123 abc

// output all properties
for (let p in state) {
  console.log(`${ p }: ${ state[p] }`);
}

// delete state
delete state.x; // or
state.x = undefined;

Get the store name:

console.log( state.stateId ); // myState

Run an event handler when any property changes:

// event handler function
function stateEventHandler(evt) {

  const d = evt.detail;
  console.log(`
    ${ d.property } has changed
    from ${ d.valueOld } to ${ d.value }
    in store ${ d.store.stateId }
    (event type "${ evt.type }")
  `);

}

// handle any state change
state.addEventListener('*', stateEventHandler);

or when an individual property changes:

// handle changes to state.a property
state.addEventListener('a', stateEventHandler);

Example:

state.a = 'one';

/*
both the "a" and "any change" events trigger - ouput:
a has changed from 1 to one in store myStore (event type "a")
a has changed from 1 to one in store myStore (event type "*")
*/

state.b = 'two';

/*
the "any change" event triggers - ouput:
b has changed from 2 to two in store myStore (event type "*")
*/

API reference

Access a named store using the asynchronous stateZx constructor with optional parameters:

name	type	description
stateId	string	state identifier (statezx if not defined)
stateDefault	object	initialization object

The initialization object can contain any number of key/value pairs, e.g.

const state = await stateZx('myState', {
  a: 1,
  b: 'two',
  c: false,
  xArray: [1,2,3],
  yObject: { p1: 'prop1', p2: 'prop2' }
});

stateZx uses previously-stored database values by default. Therefore, state.a is only set to 1 if it's undefined (or it's 1 in the store). Setting a new value triggers events, stores it in the indexedDB database, and synchronizes with other tabs/windows using stateZx on the same domain (which trigger their own events).

.stateId

Returns the state identifier (read-only):

console.log( state.stateId ); // myState

set, get, and delete properties

Set and get any property using a valid name and value:

state.prop1 = 'my first property';

console.log( state.prop1 );     // my first property
console.log( state['prop1'] );  // my first property

Delete a property:

delete state.prop1;
// or: delete state['prop1'];
// or: state.prop1 = undefined;
// or: state['prop1'] = undefined;
console.log( state.prop1 );     // undefined

Delete all properties:

for (let p in state) delete state[p];

Property:

• names can contain letters in any case, numbers, or hyphens - but must start with a letter
• values can be any native value, array, or object - but not a function

Values are checked to ensure they've changed before triggering events, storage, and tab/window synchronization. Setting state.a = 1 only has an effect when it's not already 1.

Setting properties to objects or arrays

Setting a property to an object or array will always trigger events, storage, and tab/window synchronization. This occurs because objects are passed by reference. Two objects or arrays are not the same even when their values are identical:

console.log( state.myArray );   // [1,2,3]
state.myArray = [1,2,3];        // triggers event, store, sync

console.log( state.myObject );  // {a:1,b:2}
state.myObject = {a:1,b:2};     // triggers event, store, sync

Setting a child property or array element will not trigger events, storage, and synchronization:

state.myArray.push[4];  // not handled
state.myObject.a = 99;  // not handled
state.myObject.c = 100; // not handled

It may be preferable to update the whole object or create separate stateZx stores with native values rather than use nested arrays and objects.

.set(property, value)

Sets temporary session-like values in the current tab. It does not trigger events, storage, and synchronization:

// set value
state.set('temp', 'temporary value');
console.log(state.temp); // temporary value

// delete value
state.set('temp');
console.log(state.temp); // undefined

State change events

You can trigger event handler functions when any property changes:

// handle any state change
state.addEventListener('*', stateEventHandler);

or when an individual property changes:

// handle changes to state.myProp property
state.addEventListener('myProp', stateEventHandler);

Changes to state.myProp triggers both event handlers (the more specific 'myProp' handler runs first).

The handler function receives a single object containing information about the event. Its .detail property defines an object with the following properties:

property	description
.property	name of the updated property
.value	the new value
.valueOld	the old value
.state	the state object

Example:

// event handler function
function stateEventHandler(evt) {

  const d = evt.detail;
  console.log(`stateId       : ${ d.store.stateId }`);
  console.log(`property name : ${ d.property }`);
  console.log(`new value     : ${ d.value }`);
  console.log(`previous value: ${ d.valueOld }`);

}

A state change also triggers events on other tabs and windows that use stateZx with the same store on the same domain.

Remove event handlers with the .removeEventListener() method:

state.removeEventListener('*', stateEventHandler);
state.removeEventListener('myProp', stateEventHandler);

Event and synchronization lifecycle

You can synchronously change and examine any stateZx object's properties in real time. There are no asynchronous operations other than the initial constructor.

stateZx records all property changes. A later iteration of the JavaScript event loop triggers events, updates storage, and synchronizes across tabs/windows when the CPU is idle. Consider the following code:

let counter = state.counter;

for (let i = 0; i < 1000; i++) {
  counter++;
  state.counter = counter;
}

The code will not trigger 1,000 event, storage, and synchronization processes. If state.counter is initially stored as 0, the synchronous loop will complete and it's value changes to 1000. The update process runs at some future point which:

1. triggers local events where the details object has .property set to 'counter', .oldValue set to 0, and .value set to 1000

2. updates counter in the indexedDB store to change the value from 0 to 1000

3. broadcasts a synchronization event to all tabs/windows on the same domain using stateZx which triggers identical events.

Intensive state changes do not have a significant impact on performance because stateZx makes background updates when the program is idle. Nothing would run if state.counter = 0; was added after the loop!

Usage policy

You are free to use this as you like but please do not republish it as your own work.

Please consider sponsorship if you use stateZx commercially, require support, or want new features.