Dynamic Typing

In the previous chapter, we explored JavaScript's built-in values and types and covered some of the challenges involved when using them. The next natural step is for us to explore how JavaScript's dynamic system plays out in the real world. Since JavaScript is a dynamically typed language, the variables in your code are not constrained in terms of the type of values they refer to. This introduces a huge challenge for the clean coder. Without certainty regarding our types, our code can break in unexpected ways and can become incredibly fragile. This fragility can be explained quite simply by imagining a numeric value embedded within a string:

const possiblyNumeric = '203.45';

Here, we can see that the value is numeric but that it has been wrapped in a string literal and so, as far as JavaScript is concerned, is just a regular string. But because...