JavaScript mode (i) Singleton mode

function A () {///Storage instance object Var instance;//overrides the constructor, returning only local variables within the closure instancea = function () {return instance;} The properties and methods defined on the prototype after rewriting the prototype as the instance itself are directly assigned to the instance A.prototype = this;//instantiation instance = new A ();//override constructor Instance.constructor = a;//First Instance Returns an instance of the overridden constructor after return instance;} var a = new A (), var b = new A (); Console.log (A = = B); a.prototype.xx = "1212"; Console.log (a.xx, b.xx);