text: // Interfaces
  // Type check it
  function printLabel(labelledObj) {
      console.log(labelledObj.label);
  }
  // This object fulfills the contract 
  let myObj = { size: 10, label: "Size 10 Object" };
  printLabel(myObj);
  // We would get an error if function miss-typed color for instance
  function createSquare(config) {
      let newSquare = { color: "white", area: 100 };
      if (config.color) {
          newSquare.color = config.color;
      }
      if (config.width) {
          newSquare.area = config.width * config.width;
      }
      return newSquare;
  }
  // Make a black square, but otherwise the default values
  let mySquare = createSquare({ color: "black" });
  let p1 = { x: 10, y: 20 };
  