Behold

Simple PubSub / Observers for object properties using ECMA5 getters/setters. Still very much a work in progress.

obj = { one: 1, two: 2 };
behold(obj);
behold.subscribe(obj, 'one', function(){ console.log('obj.one:',obj.one); });
obj.one = 'one';
// obj.one:one

Public API

behold(obj, [whitelist])

• obj (required): an object whose ownProperties that will be watched.
• whitelist (optional): an array of strings naming the only properties on obj we wish to track.

Returns the object provided.

behold.subscribe(obj, propertyName, fn)

Call function fn when the property propertyName on object obj changes.

Issues / Problems / Roadmap

• Requires ECMA5, so it'll work in IE9+ but not older.
• Watches only ownProperty values that are not functions/objects/arrays:
  • ownProperty functions will become expressions: o = {handle:'mattly', twitter:function(){ return "@"+this.handle } } behold(o) o.handle = 'matthewlyon' o.twitter // @matthewlyon
  • arrays will gain push/pop/slice/shift accessors: o = behold({arr: [1,2,3]}) behold.subscribe(o, 'arr', function(){ console.log(o.arr.length) }) o.arr.push(4) // 4
  • objects will track the setting of, but not their own properties.