Hey everyone, if you’ve been working with React for more than, like, five minutes, you’ve probably dabbled in Hooks—they’re basically the backbone of modern functional components, right? I run a small team that builds custom Hooks for devs tired of rewriting the same boilerplate over and over, and let me tell you: I’ve seen every mistake in the book. Whether you’re a junior dev just getting the hang of useState and useEffect, or a senior who’s been around since Class Components were the only game in town, slipping up with Hooks is way easier than you think. Let’s break down the most common mistakes I see every single day, and maybe even drop a tip or two from the side of someone who actually builds Hooks for a living. Hooks
First up, the big one that trips literally everyone: misusing useEffect. I can’t tell you how many devs I work with on our custom Hook projects who stuff every single bit of logic into useEffect like it’s a garbage can. Wait, no—actually, the mistake is two-fold here: either putting too much stuff in one useEffect, or not setting the dependency array correctly. Let’s be real, that dependency array is the worst part of Hooks. You stare at it for 10 minutes, add what you think is all the variables, and then you get that stupid linter error about missing dependencies. So a lot of people just, like, hit ignore or throw in an empty dependency array to make the error go away. Bad move. Empty dependency array means your useEffect only runs once on mount, so if that variable you’re fetching data with later updates? The useEffect never re-runs. I’ve had clients come to me because their data isn’t updating, and it’s always that empty array. Or the other way around—adding every single random variable that’s even remotely related to the component, even if it doesn’t need to trigger the effect. That causes way too many re-renders, which slows down your app to a crawl. Pro tip from my team: when we build custom data-fetching Hooks, we make sure to only include the exact variables that actually change the API call, so our users don’t have to mess with that messy dependency array.
Next mistake: overusing useState and underusing useReducer. Look, useState is great for simple stuff—like a toggle for a modal, or the value of an input. But when you have state that’s multiple related values, or it updates in complex ways (like adding/removing items from a list, or a form with 10 fields that all depend on each other), useState gets messy fast. You end up with like 5 separate useState calls, and updating them all means writing a ton of setFunction calls, and your state updates are hard to track. I see so many devs sticking with useState for these cases because they’re more comfortable with it, and that leads to tangled code. For example, if you’re building a to-do list, and you have state for the list, a new task input, whether the list is loading, and an error message—useReducer lets you bundle all that state into one object, and your updates are super predictable. My team often recommends useReducer in our Hook docs when we see projects where devs are overcomplicating state with useState, and it cuts down on so much headache.
Then there’s the issue with not memoizing values when you need to—so many devs skip useMemo and useCallback like they’re optional add-ons. Let’s be clear: useMemo and useCallback aren’t just for optimizing big apps. They’re for when you pass functions or computed values down to child components that are wrapped in React.memo. If you don’t memoize those, the child will re-render every time the parent does, even if the actual value/function didn’t change. I’ve had clients come to us with apps that have 20% more re-renders than they should, and it’s always because they forgot to memoize a callback or a computed list. The flip side here is also a mistake: over-memoizing. If you use useMemo for something that’s super cheap to compute (like adding two numbers), you’re adding extra overhead for no reason. Memoization is a tool, not a rule—use it when you actually need it, not just because you saw a tutorial say “use memo everything.”
Another super common one: mutating state directly. I swear, this is a holdover from class components where you’d modify this.state directly, but devs keep doing it with useState. Like, if you have a state array: const [todos, setTodos] = useState([]), and you try to do todos.push(newTodo) instead of setTodos([…todos, newTodo]). That’s bad! React relies on state being immutable to detect changes. When you mutate the original array, React doesn’t see a new array reference, so it doesn’t re-render your component. I’ve seen so many broken UIs because of this. The same goes for objects—mutating a state object’s property directly won’t trigger a re-render. My team’s custom state Hooks enforce immutability under the hood, so our users don’t have to remember to spread everything manually—small win, but it saves so many bugs.
Wait, let’s not forget about using Hooks inside loops, conditions, or nested functions. That’s straight up against the Rules of Hooks, right? And so many people accidentally do it. Like, putting an if statement around a useEffect call, or looping through an array and calling useState inside the loop. The Rules of Hooks exist because React relies on the order of Hooks calls to keep track of state and effects between renders. If you skip a Hook call because of a condition, or change the order, React gets confused and mixes up state for different components. I see this all the time in components that have a conditional feature—devs write an if (someCondition) { useEffect(…) } and then wonder why the state is wrong on the next render. It’s not that hard to fix: move the condition inside the useEffect, or split the component into smaller components so you’re not messing with Hook order.
Oh, and ignoring cleanup in useEffect! This is a huge one for things like API calls, event listeners, or timers. If you start a timer in useEffect, you need to clear it when the component unmounts, otherwise you get memory leaks, or the timer runs on an unmounted component and tries to update state, which throws errors. Same with API calls—if you fetch data in useEffect, and the component unmounts before the fetch finishes, you’ll get a state update on an unmounted component, which is a warning at best and a crash at worst. My team’s custom effect Hooks automatically clean up subscriptions and timers for our users, so they don’t have to write the cleanup function every time—another small thing that prevents a lot of headaches.
Wait, what about not using the functional update form of useState? Like, when you’re updating state based on the previous state value. For example, if you have a state count, and you do setCount(count + 1) inside a useEffect that runs on a button click, but if that update is happening multiple times in a row (like from a loop, or multiple event handlers), the count might not update correctly because it’s relying on the stale state value. The fix is to use the functional form: setCount(prevCount => prevCount + 1). That way you’re always working with the latest state, not the stale one from the render cycle. I see devs skipping this all the time, and they wonder why their counter is going up by 2 instead of 1 or just not updating.
And let’s talk about bad custom Hooks—wait, since I run a Hook supplier, I see so many bad custom Hooks that devs build themselves, or even use from random npm packages. A common mistake with custom Hooks is not following the same Rules of Hooks as built-in Hooks. If your custom Hook calls other Hooks, it has to be called at the top level, same as others. Also, a lot of custom Hooks are too broad or too narrow—like a Hook that only works for one specific form, or a Hook that tries to do everything and becomes bloated. My team builds custom Hooks that are generic, follow all the Rules, and are well-documented, so our users don’t have to deal with the mistakes that come from bad custom Hooks.
Another thing: not reading the values of Hooks correctly. Like, when you use a Hook that returns multiple values, and you swap them around, or not destructure them properly. For example, if a Hook returns [isLoading, data, error], and you destructure them as [data, isLoading, error], that’s a simple typo but it breaks your whole component. I see this in so many projects—devs just copy-paste the Hook usage from a tutorial and mix up the order. It’s a small mistake, but it’s so hard to track down when you’re first learning Hooks.
Wait, let’s wrap this up because I don’t want to ramble too much (but I could talk about Hooks mistakes all day). The main takeaway here is that Hooks are super powerful, but they have specific rules and best practices, and it’s easy to slip up, especially when you’re learning or working on a tight deadline. If you’re tired of fixing these same mistakes over and over in your projects, maybe it’s worth checking out custom Hooks that are built to avoid these common pitfalls—we’ve got a whole library of Hooks for data fetching, state management, side effects, and more, built by devs who’ve seen every mistake in the book. Whether you’re looking to reduce boilerplate, cut down on re-renders, or just make your code more reliable, we’ve got you covered. If you’re interested in learning more or chatting about how custom Hooks can help your team, feel free to reach out—we’re always happy to help.
References
React Official Documentation. (n.d.). Rules of Hooks. Retrieved from React.dev
Kent C. Dodds. (2020). How to use React useEffect. Retrieved from kentcdodds.com
Dan Abramov. (2019). A Complete Guide to useEffect. Retrieved from overreacted.io
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