Method update in JavaScript

methodUpdate.js

// from repl.it

function myClass() { 
  this.uniqueTask = function() { 
    return 2 
  } 
}

var obj = new myClass();
obj.uniqueTask = function() { 
  return "abc"; 
}
obj.uniqueTask();
// => 'abc'

var obj = new myClass();
obj.uniqueTask();
// => 2