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4.0.0 • Public • Published


A tiny and simple model and collection API.

  • Models act like plain old objects (that are observable for mutations)
  • Collections act like plain old arrays (that are observable for mutations)
  • Zero dependencies
  • Requires native ES2015 runtime for full feature set (needs Proxy for collection length)
  • Collections implement a stable sort
  • Similar in spirit to Backbone.Model and Backbone.Collection (or Object.observe), but designed with ES2015 in mind
  • v4.0.0 Library size: 11,909 bytes minified (2,251 bytes gzip-compressed)
  • Typescript friendly, works well with tsc --strict


npm install @srhazi/simplemodel

Basic Usage

import { Model, makeModel, Collection, makeModelCollection } from '@sufianrhazi/simplemodel';
interface Pokemon { name: string, type: string, level: number };
const pikachu = makeModel({ name: "pikachu", type: "electric", level: 17});
const squirtle = makeModel({ name: "squirtle", type: "water", level: 10});
const charmander = makeModel({ name: "charmander", type: "fire", level: 15});
const lineup = makeModelCollection([pikachu, squirtle]);
// -> models are observable by property name
squirtle.on('name', (newValue, oldValue) => {
    console.log(`squirtle's name changed from <${oldValue}> to <${newValue}>`);
// * Collections are observable for adds/removes/resets/sorts
lineup.on('add', (item, index) => {
    console.log(`${item.name} added to the group at index ${index}!`);
lineup.on('remove', (item, index) => {
    console.log(`${item.name} removed from the group! (was index ${index})`);
// * Collections that hold Models are also observable for model changes
lineup.on('change', (item, index, field, newValue, oldValue) => {
    console.log(`${item.name} (pokemon ${index}${field} changed from <${oldValue}> to <${newValue}>!`);
// * Models act just like objects
squirtle.name = squirtle.name + ', the destroyer';
// "squirtle's name changed from <squirtle> to <squirtle, the destroyer>"
// "squirtle, the destroyer (pokemon 1) name changed from <squirtle> to <squirtle, the destroyer>"
// * Why two logs? There's a 'name' handler on the model and 'change' handler on the collection.
// * Collections act just like arrays (though index access is typesafe)
lineup[0]!.level += 1;
// "pikachu (pokemon 0) level changed from <17> to <18>!"
// collections can be added to
// log: charmander added to the group at index 2!
// models can be updated atomically
    level: charmander.level + 1,
    name: "charmeleon"
// log: charmeleon's level changed from <15> to <16>!
// log: charmeleon's name changed from <charmander> to <charmeleon>!
// collections can be removed
// log: squirtle, the destroyer removed from the group! (was index 0)


  • Note: Minified standalone build depends on closure-compiler.
  • Version 4.0.0 built with
    • typescript version: 4.0.2
    • node version: v12.16.2
    • amdclean version: 2.7.0
    • Closure Compiler version: v20200517 (Built on: 2020-05-18 22:36)
  • Note: Version 4.0.0 compatible with TypeScript version 3.0.3+
  • Note: Version 3.0.1 has tests which rely on TypeScript 2.8 features (conditional types). The library should build fine in earlier versions (back to at least 2.6), but tests will not build.
  1. git clone https://github.com/sufianrhazi/simplemodel.git
  2. cd simplemodel
  3. npm install
  4. s/dist

Reference API


// A model is an object that has some additional behavior 
type Model<T> = T & ModelBehavior<T>;
interface ModelBehavior<T> {
     * Listen for a change in any single property
     * @param key the property to listen for changes on
     * @param fn
     * @returns a function that removes the listener when called
    on<K extends keyof T>(key: keyof T, fn: ModelChangeHandler<T, K>): () => void;
     * Listen for a change to any property
     * @param fn
     * @returns a function that removes the listener when called
    onAny(fn: ModelAnyChangeHandler<T>): () => void;
     * Remove all listeners
    offAll(): void;
     * Update multiple properties atomically
     * @param subset subset of properties to update at once
    update(subset: Partial<T>): void;


A collection behaves almost like arrays that also have observable behavior. There are two types of collections:

  1. makeSimpleCollection<T>(items: T[], cmp: (a: T, b: T) => number): SimpleCollection<T> - observable (and sorted) list of any type of objects
  2. makeModelCollection<T>(items: Model<T>[], cmp: (a: T, b: T) => number): ModelCollection<T> - observable (and sorted) list of model objects

In addition to add, remove, and reset events, ModelCollection<T> objects also emit change events when a particular model within it changes.

There are a few quirks to collections:

  • A collection may be sorted by providing a comparison function upon creation
    • Sort order is preserved upon addition. Newly added items will be inserted in sort order
    • If items are mutated, sort order is not preserved, you must call .sort() to re-sort the collection.
    • The comparison function can be set and cleared via calling .sort(fn) / .sort(undefined)
    • If sorted, inserts are performed via binary search, which adds O(lg(n)) comparisons in addition to the overhead of resizing the underying array via .splice()

The following methods typical in arrays are not implemented:

  • .copyWithin()
  • .fill()
  • .keys()
  • .reverse()
  • .splice()
  • .values()
// A collection is an array that has some additional behavior
type ModelCollection<T> = ArrayIsh<T> & {
     * Listen for items added to this collection
     * @returns a function that removes the listener when called
    on(name: 'add', handler: (item: T, index: number) => void): () => void;
     * Listen for items removed from this collection
     * @returns a function that removes the listener when called
    on(name: 'remove', handler: (item: T, index: number) => void): () => void;
     * Listen for a complete replacement of items in collection
     * @returns a function that removes the listener when called
    on(name: 'reset', handler: () => void)): () => void;
     * Listen for a complete sort of items in collection
     * @returns a function that removes the listener when called
    on(name: 'sort', handler: () => void)): () => void;
     * If the collection contains Model instances, listen for changes to any
     * of the Models in the collection.
     * @returns a function that removes the listener when called
    on(name: 'change', handler: (item: T, index: number, field: keyof T, curr: T[typeof field], prev: T[typeof field]) => void): () => void;
     * Listen for any change to the set of items in this collection
     * @returns a function that removes the listener when called
    onAny(handler: () => void)): () => void;
     * Remove all listeners
    offAll(): void;
     * Add a Model to the collection.
     * If sorted, the item will be placed at the correctly sorted index.
    add(item: T): void;
     * Remove an item from the collection
     * @returns true if an item was removed
    remove(item: T): boolean;
     * Remove an item at a specific index
     * @param index the index to remove
     * @returns true if an item is removed
    removeAt(index: number): boolean;
     * Replace all items in the collection
     * @param newItems the replacement items
    reset(newItems: T[]): void;


npm i @srhazi/simplemodel

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