gistfile1.js

function Car () {
  this.color = 'red';
  //alert('car was made');
}


function Truck () {
  // how do I call the parent constructor (i.e. make the alert box appear)
  this.color = 'blue';
}

Truck.prototype = new Car();

Truck.prototype.wheels = 4;

t = new Truck();
alert(t.wheels);