gistfile1.txt

var SomeClassClosure = function() {
  this.method = function() {}
}

new SomeClassClosure
// {method: fnA()}
new SomeClassClosure
// {method: fnB()} // a new fn is allocated each time

var SomeClassPrototype = function() {}
SomeClassPrototype.prototype.method = function() {}

new SomeClassPrototype
// {__proto__: SomeClassPrototype.prototype}
new SomeClassPrototype
// {__proto__: SomeClassPrototype.prototype}
// method is shared between the two instances