/**
* Wrap object in a proxy, that calls callback
* anytime a property is set, passing the property name as parameter.
* Note that this doesn't modify any variable that pointer towards object,
* so this is _not_ equivalent to replacing the target object with a proxy.
*/
function _watch(object, callback)
{
return new Proxy(object, {
"get": (obj, key) => {
return obj[key];
},
"set": (obj, key, value) => {
obj[key] = value;
callback(key);
return true;
}
});
}
/**
* Inherit from AutoWatcher to make 'this' a proxy object that
* watches for its own property changes and calls the method given
* (takes a string because 'this' is unavailable when calling 'super').
* This can be used to e.g. automatically call a rendering function
* if a property is changed.
* Using inheritance is necessary because 'this' is immutable,
* and isn't defined in the class constructor _unless_ super() is called.
* (thus you can't do something like this = new Proxy(this) at the end).
*/
class AutoWatcher
{
constructor(method_name)
{
this._ready = false;
return _watch(this, () => this._ready && this[method_name]());
}
}