Deep Observer

Tiny Object Observe library ( < 100bytes gziped), to deep watch and track changes in Objects and Arrays. The provided callback to the Constuctor is executed each time a change is deteced, recieving a complete set of data relative to the detected change.

• Deep Observation ( configurable Depth )
• Optional construction observe
• Compatible with all JS primitive types
• No dependencies
• Wide platform support :
  • Node
  • Chrome 49
  • Firefox 34
  • Edge 14
  • Opera 36
  • Safari 10

Syntax

1. Constructor

When at least two arguments are passed to Observer() , it behaves as a Constructor :

new Observer( object , callback [, config] )

• object: Object to observe
• callback : Function to be invoked on object changes
• config : (optional) Object
  • id : Unique string to use as identifier to the Observable. (if not provided is generated automatically)
  • observeConstruction : Boolean. If true callback will be executed also in construction stage. (default: false)
  • depth : Integer. Sets the observing depth limit. When set to 0, no limit is applied (default : 0 )
  • ignoreSameValueReassign : Boolean. By default callback is only executed when the assigned value differs from the previous one. When this option is set to false, callback function is executed always ( default : true )

Returns : an Observable (Proxy)

Note : deep-observer DOES NOT perform changes in the original provided Object. The observation is performed in the Observable returned Object.

2. Getter

When only a String is provided to Observer() it behaves as a getter :

Observer( id )

• ìd: String provided previously in the constructor config object

Returns : the matching Observable (Proxy) or undefined

3. Callback function

The function called each time changes are made, will receive an event object containng the following properties :

• action : String containing one of the following values : add|update|delete
• object: Affected property parent's Object
• name: Name of the modified property (or array index)
• oldValue : Value of the property before the change
• keypath : String representing the internal path to the affected property.

Basic usage example

Provide to the constructor an object and a callback, and perform a change on the object, to see how the callback is triggered:

   // create an observable object
   const myObserved = new Observer( { a : 12 } , e=>console.log('changed!' , e) );
   // perform a modification
   myObserved.a = 14; 
   // console outputs : 'changed!' { action:'update', oldValue:12, object:{a:14}, name:'a' }

Advanced usage example

An example of new Observer using all the configuration parameters

   // create an observable object
   const myObserved = new Observer( 
       { a : 12 } ,   // object to abserve
       e=>console.log('changed!' , e) ,  // callback
       {
           id : 'observed_1', // observable internal id  
           depth : 5, // observe maximum 6 levels of depth
           observeConstruction : true , // execute callback on construction
           ignoreSameValueReassign : false // call callback always
       }
   );
   // because observeConstruction=true, callback fuction is executed...
   // console outputs : 'changed!' { action:'add', keypath : 'observed_1.a.' , oldValue:undefined, object:{a:12}, name:'a' }
   // perform a modification...
   myObserved.a = 14; 
   // console outputs : 'changed!' { action:'update', keypath : 'observed_1.a.' , oldValue:12, object:{a:14}, name:'a' }
   // retrieve the observable...
   const sameObserved = Observer('observed_1');
   console.log( myObserved === sameObserved );
   // console outputs : true

Package distribution :

In browser enviroment you can include this library using the jsdelivr CDN ...

<script src='https://cdn.jsdelivr.net/gh/colxi/deep-observer@latest/src/deep-observer.min.js'></script>

If you are in the NodeJs enviroment, can install the package via:

$ npm install deep-observer --save

Licence

GPL 3