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React performance hacks

Posted on:May 3, 2022 at 07:11 PM

While working on my small “SaaS” product, I wanted to make it as “performant” as it gets. Something I found out is that every time I do a re-render while using useEffect the dependency array is being re initialized every time. So what we can do to mitigate this is adding a empty array varible and assigning it to the useEffect.

For example if you have something like this:

useEffect(() => {
  // some code
}, []);

You can write something like:

const empy = []; // Must be outside the component declaration / global variable

useEffect(() => {
  // some code
}, empty);

So now we have only one initialization of the empty array.

useMemo / useCallback

Something else which is useful for performance gains in React are some specific hooks like the useMemo hook Documentation link.

In layman terms, what this does is not rendering a child component in the case of not changing the child component’s internal state. We Just render the parent component. So we can save a lot of rendering time with this method.

useCallback hook Documentation link similar to the useMemo hook, we can use useCallback instead of useEffect which will only trigger when one of the dependencies change and return us a Memoized / cached callback.

Some small optimizations tips I’ve been using recently for React. I’m on a quest to learn even more things about the way react optimization works as I find this part of React still lacking a bit from my side. Will update with further findings.