How to Optimize React Components Using Computed Variables


30 Mar, 2023

React, like a high-speed jet ski, boasts of its reactive state variables and props that allow you to zip around your app with lightning-fast agility. But what if I told you that you could make your app even faster? Get ready to strap on your racing goggles as we dive into the world of computed variables.

Computed Variables in React

In React, a computed variable is a value that is derived from or computed based on one or more state variables. It is similar to a computed property in other frameworks, such as Vue.js or Knockout.js. Computed variables are created using hooks like useMemo or useCallback, and their value is only recomputed when their dependencies change. This allows for a more efficient rendering process, since the component doesn't need to re-render every time a state variable changes, but only when the computed variable changes. In other words, computed variables act as a kind of pit stop, where the component can swap out a slow state variable for a speedy computed one. This can help eliminate unnecessary re-renders and make your app faster than a cheetah on a jet ski, especially in complex applications where performance is critical.

Some code please

Let's take a look at an example. Say you have a component that renders a list of items, and you want to display the total number of items in the list. You could use a computed variable to achieve this:

const [items, setItems] = useState([]); // usememo is not necessary here, but it's good practice // if itemCount is a computation heavy value, we can memoize it const itemCount = useMemo(() => items.length, [items]);

By using useMemo, we can create a memoized version of the itemCount variable. This means that the value of itemCount will only be computed when the items state variable changes, which can help eliminate unnecessary re-renders and make your app faster than a jet-propelled cheetah.

Conclusion: The Fast and the Furious

In conclusion, computed variables can help make your React app faster than a cheetah on a jet ski. By identifying which state variables are computed values and replacing them with normal variables, you can improve your app's performance and leave your competitors in the dust. So, buckle up and get ready to leave your competition in the rear-view mirror with these React performance optimisation techniques and coding standards!

That's it for now, thanks for reading! You can find me at @samuellawrentz on X.

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