Proxy-observable NPM

proxy-observable

ES6 Proxy observable implementation. Supports Arrays and Objects

Attention!

Please keep in mind that the implementation is based on ES6 Proxy feature which is a very slow thingy

Lib Size

Install

npm install proxy-observable --save

Usage

Just call observable() if you want an object or an array to be observable

API

import observable from "proxy-observable";

const soldier = {
  name: "Titus Pullo",
  age: 36,
  inventory: observable({
    sword: "Dagger",
    coins: 0
  }),
  friends: observable(["Gaius Octavian"])
};

console.log(JSON.stringify(soldier, null, 2));

{
  "name": "Titus Pullo",
  "age": 36,
  "inventory": {
    "sword": "Dagger",
    "coins": 0
  },
  "friends": [
    "Gaius Octavian"
  ]
}

Object

const onCoinsChanged = 
  soldier.inventory.on("coins", (value, prev) => {
    console.log(value, prev); // 100 0
  });
soldier.inventory.coins = 100; // onCoinsChanged will be called
soldier.inventory.off(onCoinsChanged);

Simply speaking soldier.inventory is still just a simple object, but it has additionally a few things:

method on Attach a handler to an event for the elements
method once Attach a handler to an event for the elements. The handler is executed at most once per element per event type
method off Remove an event handler
you can call just soldier.inventory.newProp = value to define a new prop, instead of soldier.inventory["newProp"] = value

Array

soldier.friends.on("change", item => {
  console.log(item); // "Lucius Vorenus" twice
});
soldier.friends.on("shift", item => {
  console.log(item); // "Gaius Octavian"
});
soldier.friends.push("Lucius Vorenus"); 
soldier.friends[0] = "Lucius Vorenus"
soldier.friends.shift();

soldier.friends is still just a simple array with on, once and off methods and predefined events

Array events

change - Fires when an item in an array is changed:

arr[0] = "new value";
// or
arr.push("new value");

pop - Fires when pop method is called:

arr.pop();

shift - Fires when shift method is called:

arr.shift();

any other Array's methods

`any` event

Do you want to track all the events? Just use any like this:

// object
soldier.inventory.on("any", (value, prev, prop) => {
  console.log(prop); // "coins", "shield"
});
soldier.inventory.coins = 1000;
// This way you can track when a new property is added to an object
soldier.inventory.shield = "Gold Shield"; 

// array
soldier.friends.on("any", (value, prev, e) => {
  // e is "change", "pop", "shift" or any other method of Array
  console.log(e); 
});
soldier.friends[0] = "Mark Antony";
soldier.friends.pop();

Browser Usage

<!-- ES6 not minified version -->
<script src="../node_modules/proxy-observable/bin/proxy.observable.es6.js"></script>
<!-- ES5 minified version -->
<!--<script src="../node_modules/proxy-observable/bin/proxy.observable.min.js"></script>-->

<script>
  const soldier = {
    name: "Titus Pullo",
    age: 36,
    inventory: observable({
      sword: "Dagger",
      coins: 0
    })
  };

  console.log(soldier.inventory.coins); // 0
  soldier.inventory.on("coins", (value, prev) => {
    console.log(value, prev); // 100 0
  });
  soldier.inventory.coins = 100;
</script>

One more example

const Frodo = observable({
  name: "Frodo Baggins",
  bag: observable([]),
  friends: observable([])
});

const Samwise = {
  name: "Samwise Gamgee",
  friends: [Frodo]
};

Frodo.friends.on("change", friend => {
  console.log(`Frodo has a new friend ${friend.name}! Cograts!`);
});

Frodo.bag.on("any", (item, prev, e) => {
  if (e === "change") {
    console.log("Frodo got a new item: " + item);
    if (item === "ring") {
      console.log("Oh! My Precious!");
    }
  } else if (e === "pop" || e === "shift"){
    console.log("Frodo lost an item: " + item);
    if (item === "ring") {
      console.log("Gollum! I'm coming to get you!");
    }        
  }
});

Frodo.friends.push(Samwise);
Frodo.bag.push("apple");
Frodo.bag.push("ring");
Frodo.bag.pop();
Frodo.friends.pop();