Advanced TypeScript Programming Projects

Using different types with union types

The first feature that we are going to look at is one of my favorites, that is, the ability to use union types. These types are used when a function expects a single parameter to be one type or another. Suppose, for instance, that we have a validation routine that needs to check whether a value is in a particular range and this validation could receive the value either from a textbox as a string value, or as a number value from a calculation. As each of the techniques for solving this issue have a lot in common, we'll start off with a simple class that allows us to specify the minimum and maximum values that form our range and a function to actually perform the validation, as follows:

class RangeValidationBase ...