descriptor.js

var Klass = function(text){ this.text = text; };
Klass.prototype.method1 = function(){ return this.text + 'のメソッド' };

var descriptor = Object.getOwnPropertyDescriptor(Klass.prototype, 'method1')
  , originalFunction = descriptor.value;
descriptor.value = function(){ console.warn('method1 is deprecated'); return originalFunction.apply(this); };
Object.defineProperty(Klass.prototype, 'method1', descriptor);

console.log(new Klass('メソッド1').method1());

descriptor2.js

var Klass = function(text){ this.text = text; };
Klass.prototype.method1 = function(){ return this.text + 'のメソッド' };

var k = new Klass('メソッド1');

var descriptor = Object.getOwnPropertyDescriptor(Klass.prototype, 'method1')
  , originalFunction = descriptor.value;
descriptor.value = function(){ console.warn('method1 is deprecated'); return originalFunction.apply(this); };
Object.defineProperty(Klass.prototype, 'method1', descriptor);

console.log(k.method1());