Observing proxy
A proxy for observing object state changes.
This module is based on the Object.defineProperty method and serves as an interface to the user provided object, notifying subscribers about the user object changes.
var obj={person:'Eddie',age:22};
_o.onUpdate(obj,{
age:function(value){
if(value>this.oldValue)
console.log('Happy birthday, Peter!')
},
person:function(value){
console.log(this.oldValue+' is now '+value);
}
});
_o(obj).person='Peter';
//> Eddie is now Peter
_o(obj).age++;
//> Happy birthday, Peter!Install
npm install observingproxy
or
bower install observingproxy
Advanced usage (implemented with Object.observe in mind)
var obj={person:'Peter',age:22};
_o.observe(obj,function(changes){
for(var i=0;i<changes.length;i++)
if(changes[i].name==='age')
if(changes[i].object.age>changes[i].oldValue)
console.log('Happy birthday, Peter!')
});
_o(obj).age++;
//> Happy birthday, Peter!Note: it works only with property
update.addordeleteoperations are not supported.
With arrays
var arr=[1,2,3];
_o.observe(arr,function(changes){
for(var i=0;i<changes.length;i++)
if(changes[i].type==='splice')
console.log('Array changed')
});
_o(arr).push(4);
//> Array changedError handling and destructor
var observer=_o.onUpdate(null,'name',function(value){
//...
});
// Throw observation exception here
try{
observer.report();
}
catch(e){throw e}
// Observing proxy error: target is null
// Destroy your observer
observer.destroy();Deferred observer notification
While proxy applies property modification immediately, it sends the observer notification call to the end of execution thread using setTimeout method as a wrapper.
So now, if you do
_o.observe(obj,function(changes){
// iterate changes
});
_o(obj).p1=1;
_o(obj).p2=2;
_o(obj).p3=3;observer is notified only once with changes argument containing latest modifications. It makes observer a load sustainable to an observed object being intensively modified.
