Using Calculated Variables

So far, we've learned how to create reactive states with useState, or how to use props to pass data to a component.

But sometimes you need to derive a value from what you already have, for example:

• Calculating a total from an array of prices
• Displaying different text depending on usage
• Etc...

These intermediate variables are computed (or derived) variables: they are not directly stored in the state, but are dynamically generated from other values.

Let's imagine an application where we know a first name and an age, and we want to display a complete sentence: