Problem Statement: In TypeScript 1.1, there are two basic ways to initialize complex properties with strong typing via a parameterized class constructor. Both have disadvantages. I will illustrate this with a simple example that uses Knockout, but this issue applies to any other JavaScript library that implements complex objects via initializer functions.
"Method 1" is to instantiate the properties outside of the constructor using a throw-away value, and then to set the desired value inside the constructor (see RightTriangle1 below). This method has the advantage of being rather simple to program/maintain because TypeScript automatically infers the property's type. However, this has the potential to cause ripple effects or performance issues at runtime because the code to instantiate each property is run at least twice.
class RightTriangle1 {
public height = ko.observable(0);
public width = ko.observable(0);
public hypotenuse = ko.computed(() => {
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