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Polyfill for the Object.watch/Object.unwatch functions available in Mozilla browsers
/*
Polyfill for the Object.watch/Object.unwatch functions available in Mozilla browsers
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Object/watch
you have a test here:
http://www.telecable.es/personales/covam1/deployToNenyures/SourceCode/Object.watch.test.js
and can read more here:
http://deploytonenyures.blogspot.com.es/2013/02/objectwatch-polyfill.html
*/
if (!Object.prototype.watch) {
Object.prototype.watch = function(prop, handler){
var desc = Object.getOwnPropertyDescriptor(this, prop);
var newGet;
var newSet;
//these cases make little sense, so do nothing we won't be watching readonly descriptors
if (!desc.configurable
|| (desc.value === undefined && !desc.set)
|| desc.writable === false)
return;
if (desc.value){
var val = desc.value;
newGet = function(){
return val;
};
newSet = function(newVal){
val = handler.call(this, prop, val, newVal);
};
//let's leverage the setter to store initial information to enable "unwatch"
newSet._watchHelper = {
initialType: "dataDescriptor"
};
}
else{
newGet = desc.get;
newSet = function(newVal){
val = handler.call(this, prop, val, newVal);
desc.set.call(this, val);
};
newSet._watchHelper = {
initialType: "accessorDescriptor",
oldDesc: desc
};
}
Object.defineProperty(this, prop, {
get: newGet,
set: newSet,
configurable: true,
enumerable: desc.enumerable
});
};
Object.prototype.unwatch = function(prop){
var desc = Object.getOwnPropertyDescriptor(this, prop);
if (desc.set._watchHelper){
if(desc.set._watchHelper.initialType == "dataDescriptor"){
Object.defineProperty(this, prop, {
value: this[prop],
enumerable: desc.enumerable,
configurable: true,
writable: true
});
}
else{
Object.defineProperty(this, prop, {
get: desc.get,
set: desc.set._watchHelper.oldDesc.set,
enumerable: desc.enumerable,
configurable: true
});
}
}
};
}
@mhils

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commented Apr 4, 2013

This is a great improvement over the initial version, thank you very much.
Would you mind licensing it under MIT and add an appropriate license header? http://en.wikipedia.org/wiki/MIT_License#License_terms

@abbood

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commented Mar 1, 2014

i'm not sure how the test script works.. how are we supposed to test this?

@adriengibrat

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commented Jul 20, 2014

I've rewrote this, optimized for minification + included some tests :
https://gist.github.com/adriengibrat/b0ee333dc1b058a22b66

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