Code_to_test.js

var greet = function(callback) {
  var todaysGreeting = "Hello, ";
  callback(todaysGreeting);
}

var Greeter = function(name) {
  this.name = name;
  this.sa;  
  this.sal = function(sa){
      
    this.sa = sa;
    console.log(this.sa)
  }
  new greet(this.sal);     
  this.run =  function (){
    alert(this.sa + this.name);
  }  
}

var abc = new Greeter("world!")
abc.run();