In instanceProto.onCreate = function()
Make a variable this.confirmation = false;
In cnds.ConfirmOKclicked
return this.confirmation;
this. makes that the variable is intriseque part of the plugin's runtime and its value is stored over the several blocks of code.
The use of variable (their declaration and use) is directly tied to javascript.
this. is also a "standard function" of Javascript.
The SDK builds on this to make you use
this.variable_name; to store your values and have access to them within the plugin, even once it is sealed.
This is covered in the SDK - extract.