Enumerating over all the properties in an object. Find out whats in there.

for-in.js

//create the object with properties & values.
var myCar = new Object();
myCar.make = "Ford";
myCar.model = "Mustang";
myCar.year = 1969;

//then LOOP(enumerate) through all the properties of the object myCar
function showProps(obj, objName) {
  var result = "";
  for (var i in obj) {
    if (obj.hasOwnProperty(i)) {
        result += objName + "." + i + " = " + obj[i] + "\n";
    }
  }
  return result;
}

//then call it
showProps(myCar, "myCar")

This is mainly used within the console to see what properties you have access to within the object.