How to fix missing dependency warning when using useEffect React Hook

Question

With React 16.8.6 (it was good on previous version 16.8.3), I get this error when I attempt to prevent an infinite loop on a fetch request:

./src/components/BusinessesList.js
Line 51:  React Hook useEffect has a missing dependency: 'fetchBusinesses'.
Either include it or remove the dependency array  react-hooks/exhaustive-deps

I've been unable to find a solution that stops the infinite loop. I want to stay away from using useReducer(). I did find this discussion [ESLint] Feedback for 'exhaustive-deps' lint rule #14920 where a possible solution is You can always // eslint-disable-next-line react-hooks/exhaustive-deps if you think you know what you're doing. I'm not confident in what I'm doing, so I haven't tried implementing it just yet.

I have this current setup, React hook useEffect runs continuously forever/infinite loop and the only comment is about useCallback() which I'm not familiar with.

How I'm currently using useEffect() (which I only want to run once in the beginning similar to componentDidMount()):

useEffect(() => {
    fetchBusinesses();
  }, []);

const fetchBusinesses = () => {
    return fetch("theURL", {method: "GET"}
    )
      .then(res => normalizeResponseErrors(res))
      .then(res => {
        return res.json();
      })
      .then(rcvdBusinesses => {
        // some stuff
      })
      .catch(err => {
        // some error handling
      });
  };

Answer 1

If you aren't using fetchBusinesses method anywhere apart from the effect, you could simply move it into the effect and avoid the warning

useEffect(() => {
    const fetchBusinesses = () => {
       return fetch("theURL", {method: "GET"}
    )
      .then(res => normalizeResponseErrors(res))
      .then(res => {
        return res.json();
      })
      .then(rcvdBusinesses => {
        // some stuff
      })
      .catch(err => {
        // some error handling
      });
  };
  fetchBusinesses();
}, []);

If however you are using fetchBusinesses outside of the effect, you must note two things

1. Is there any issue with you not passing fetchBusinesses as a method when it's used during mount with its enclosing closure?
2. Does your method depend on some variables which it receives from its enclosing closure? This is not the case for you.
3. On every render, fetchBusinesses will be re-created and hence passing it to useEffect will cause issues. So first you must memoize fetchBusinesses if you were to pass it to the dependency array.

To sum it up I would say that if you are using fetchBusinesses outside of useEffect you can disable the rule using // eslint-disable-next-line react-hooks/exhaustive-deps otherwise you can move the method inside of useEffect

To disable the rule you would write it like

useEffect(() => {
   // other code
   ...
 
   // eslint-disable-next-line react-hooks/exhaustive-deps
}, []) 

Answer 2

There are very good options for state management librariess if you are creating a new app or have enough flexibility. Check out Recoil.

Just for completeness:

1. (Stopped working) Use function as useEffect callback

useEffect(fetchBusinesses, [])

2. Declare function inside useEffect()

useEffect(() => {
  function fetchBusinesses() {
    ...
  }
  fetchBusinesses()
}, [])

3. Memoize with useCallback()

In this case, if you have dependencies in your function, you will have to include them in the useCallback dependencies array and this will trigger the useEffect again if the function's params change. Besides, it is a lot of boilerplate... So just pass the function directly to useEffect as in 1. useEffect(fetchBusinesses, []).

const fetchBusinesses = useCallback(() => {
  ...
}, [])
useEffect(() => {
  fetchBusinesses()
}, [fetchBusinesses])

4. Function's default argument

As suggested by Behnam Azimi

It's not best practice, but it could be useful in some cases.

useEffect((fetchBusinesses = fetchBusinesses) => {
   fetchBusinesses();
}, []);

5. Create a custom hook

Create a custom hook and call it when you need to run function only once. It may be cleaner. You can also return a callback to reset re-run the "initialization" when need.

// customHooks.js
const useInit = (callback, ...args) => {
  const [mounted, setMounted] = useState(false)
  
  const resetInit = () => setMounted(false)

  useEffect(() => {
     if(!mounted) {
        setMounted(true);
        callback(...args);
     }
  },[mounted, callback]);

  return [resetInit]
}

// Component.js
return ({ fetchBusiness, arg1, arg2, requiresRefetch }) => {
  const [resetInit] = useInit(fetchBusiness, arg1, arg2)

  useEffect(() => {
    resetInit()
  }, [requiresRefetch, resetInit]);

6. Disable eslint's warning

Disabling warnings should be your last resort, but when you do, better do it inline and explicitly, because future developers may be confused or create unexpected bugs without knowing linting is off

useEffect(() => {
  fetchBusinesses()
}, []) // eslint-disable-line react-hooks/exhaustive-deps

Answer 3

./src/components/BusinessesList.js
Line 51:  React Hook useEffect has a missing dependency: 'fetchBusinesses'.
Either include it or remove the dependency array  react-hooks/exhaustive-deps

It's not a JavaScript/React error, but an ESLint (eslint-plugin-react-hooks) warning.

It's telling you that the hook depends on function fetchBusinesses, so you should pass it as a dependency.

useEffect(() => {
  fetchBusinesses();
}, [fetchBusinesses]);

It could result in invoking the function on every render if the function is declared in a component like:

const Component = () => {
  /*...*/

  // New function declaration every render
  const fetchBusinesses = () => {
    fetch('/api/businesses/')
      .then(...)
  }

  useEffect(() => {
    fetchBusinesses();
  }, [fetchBusinesses]);

  /*...*/
}

because every time the function is redeclared with a new reference.

The correct way of doing this stuff is:

const Component = () => {
  /*...*/

  // Keep the function reference
  const fetchBusinesses = useCallback(() => {
    fetch('/api/businesses/')
      .then(...)
  }, [/* Additional dependencies */])

  useEffect(() => {
    fetchBusinesses();
  }, [fetchBusinesses]);

  /*...*/
}

Or just define the function in useEffect.

More: [ESLint] Feedback for 'exhaustive-deps' lint rule #14920

Answer 4

These warnings are very helpful for finding components that do not update consistently: Is it safe to omit functions from the list of dependencies?.

However, if you want to remove the warnings throughout your project, you can add this to your ESLint configuration:

  {
  "plugins": ["react-hooks"],
  "rules": {
    "react-hooks/exhaustive-deps": 0
    }
  }

Answer 5

The solution is also given by React. They advice you use useCallback which will return a memoize version of your function:

The 'fetchBusinesses' function makes the dependencies of the useEffect Hook (at line NN) change on every render. To fix this, wrap the 'fetchBusinesses' definition into its own useCallback() Hook react-hooks/exhaustive-deps

useCallback is simple to use as it has the same signature as useEffect. The difference is that useCallback returns a function. It would look like this:

 const fetchBusinesses = useCallback( () => {
        return fetch("theURL", {method: "GET"}
    )
    .then(() => { /* Some stuff */ })
    .catch(() => { /* Some error handling */ })
  }, [/* deps */])
  // We have a first effect that uses fetchBusinesses
  useEffect(() => {
    // Do things and then fetchBusinesses
    fetchBusinesses();
  }, [fetchBusinesses]);
   // We can have many effects that use fetchBusinesses
  useEffect(() => {
    // Do other things and then fetchBusinesses
    fetchBusinesses();
  }, [fetchBusinesses]);

Answer 6

const [mount, setMount] = useState(false)
const fetchBusinesses = () => {
   // Function definition
}
useEffect(() => {
   if(!mount) {
      setMount(true);
      fetchBusinesses();
   }
},[fetchBusinesses, mount]);

This is solution is pretty simple and you don't need to override ESLint warnings. Just maintain a flag to check whether the component is mounted or not.

Answer 7

Just disable ESLint for the next line;

useEffect(() => {
   fetchBusinesses();
// eslint-disable-next-line
}, []);

In this way, you are using it just like a component did mount (called once).

updated

or

const fetchBusinesses = useCallback(() => {
 // Your logic in here
 }, [someDeps])

useEffect(() => {
   fetchBusinesses();
// No need to skip the ESLint warning
}, [fetchBusinesses]);

fetchBusinesses will be called every time someDeps changes.

Answer 8

This article is a good primer on fetching data with hooks: https://www.robinwieruch.de/react-hooks-fetch-data/

Essentially, include the fetch function definition inside useEffect:

useEffect(() => {
  const fetchBusinesses = () => {
    return fetch("theUrl"...
      // ...your fetch implementation
    );
  }

  fetchBusinesses();
}, []);

Answer 9

You try this way:

const fetchBusinesses = () => {
    return fetch("theURL", {method: "GET"})
        .then(res => normalizeResponseErrors(res))
        .then(res => {
            return res.json();
        })
        .then(rcvdBusinesses => {
            // Some stuff
        })
        .catch(err => {
            // Some error handling
        });
  };

and

useEffect(() => {
    fetchBusinesses();
});

It works for you.

But my suggestion is try this way and it also works for you. It's better than the previous way. I use it this way:

useEffect(() => {
    const fetchBusinesses = () => {
        return fetch("theURL", {method: "GET"})
            .then(res => normalizeResponseErrors(res))
            .then(res => {
                return res.json();
            })
            .then(rcvdBusinesses => {
                // Some stuff
            })
            .catch(err => {
                // Some error handling
            });
    };

    fetchBusinesses();
}, []);

If you get data on the base of a specific id, then add in callback useEffect [id]. Then it cannot show you the warning React Hook useEffect has a missing dependency: 'any thing'. Either include it or remove the dependency array

Answer 10

Actually the warnings are very useful when you develop with hooks. But in some cases, it can needle you. Especially when you do not need to listen for dependencies change.

If you don't want to put fetchBusinesses inside the hook's dependencies, you can simply pass it as an argument to the hook's callback and set the main fetchBusinesses as the default value for it like this:

useEffect((fetchBusinesses = fetchBusinesses) => {
   fetchBusinesses();
}, []);

It's not best practice, but it could be useful in some cases.

Also, as Shubham wrote, you can add the below code to tell ESLint to ignore the checking for your hook.

// eslint-disable-next-line react-hooks/exhaustive-deps

Answer 11

Well, if you want to look into this differently, you just need to know what options React has that are non exhaustive-deps. One of the reason you should not use a closure function inside the effect is on every render, it will be recreated/destroyed again.

So there are multiple React methods in hooks that are considered stable and non-exhausted where you do not have to apply to the useEffect dependencies, and in turn will not break the rules engagement of react-hooks/exhaustive-deps. For example, the second return variable of useReducer or useState which is a function.

const [,dispatch] = useReducer(reducer, {});

useEffect(() => {
    dispatch(); // Non-exhausted - ESLint won't nag about this
}, []);

So in turn, you can have all your external dependencies coexist with your current dependencies within your reducer function.

const [,dispatch] = useReducer((current, update) => {
    const { foobar } = update;
    // Logic

    return { ...current, ...update };
}), {});

const [foobar, setFoobar] = useState(false);

useEffect(() => {
    dispatch({ foobar }); // non-exhausted `dispatch` function
}, [foobar]);

Answer 12

In my case, it had this warning with my local variable organization, and when I put organization in the dependency array, useEffect would fetch infinitely. Therefore if you have some problems like mine, use useEffect with the dependency array and split:

Because if you have multiple API calls that modify state, it invokes useEffect multiple times.

From:

  const { organization } = useSelector(withOrganization)
  const dispatch = useDispatch()

  useEffect(() => {
    dispatch(getOrganization({}))
    dispatch(getSettings({}))
    dispatch(getMembers({}))
  }, [dispatch, organization])

To:

  const { organization } = useSelector(withOrganization)
  const dispatch = useDispatch()

  useEffect(() => {
    dispatch(getOrganization({}))
    dispatch(getSettings({}))
  }, [dispatch, organization])

  useEffect(() => {
    dispatch(getMembers({}))
  }, [dispatch])

Answer 13

This is not an answer specific to the question use case but more general case, and cover the case when useEffect or extract and import is not warking. The useRef senario:

Sometimes the scenario is that useEffect should have the empty array and you still want to use inside the useEffect parts of the state but still you don't want inject them as dependencies, also you might tried the useCallback and now react is complains about the dependencies of the useCallback and you stuck. In this case in some cases you can use useRef. for example:

const locationRef = useRef(location);
useEffect(()=>{
const qs = locationRef.current.search
...
},[])

You should be careful when using this technique and be aware of that useRef is not activate a render process.

Answer 14

You can remove the second argument type array [], but the fetchBusinesses() will also be called on every update. You can add an IF statement into the fetchBusinesses() implementation if you like.

React.useEffect(() => {
  fetchBusinesses();
});

The other one is to implement the fetchBusinesses() function outside your component. Just don't forget to pass any dependency arguments to your fetchBusinesses(dependency) call, if any.

function fetchBusinesses (fetch) {
  return fetch("theURL", { method: "GET" })
    .then(res => normalizeResponseErrors(res))
    .then(res => res.json())
    .then(rcvdBusinesses => {
      // some stuff
    })
    .catch(err => {
      // some error handling
    });
}

function YourComponent (props) {
  const { fetch } = props;

  React.useEffect(() => {
    fetchBusinesses(fetch);
  }, [fetch]);

  // ...
}

Answer 15

If you want to disable this useless message, just add this at the begining of your file.

/* eslint-disable react-hooks/exhaustive-deps */

This will disable the warning for the entire file.

Answer 16

This warning happens, if variables that you are using inside useEffect are defined inside the component or passed to the component as a prop. Since you defined fetchBusinesses() inside same component, and eslint follows that rule, you have to pass it to the dependency array. But in your case, just passing [] would also work

In this case it will work, but what if fetchBusinesses was using setState inside the function and calling it would rererender the component, therefore your fetchBusinesses would change so useEffect would run which would create an infinite loop. So just blindly following the eslint might cause extra bugs.

Solution for your use case to make eslint happy, using useCallback with an [].

const memoizedFetchBusinesses=useCallback(
        fetchBusinesses,
        [] // unlike useEffect you always have to pass a dependency array
       )

When your component first renders, a function referred as fetchBusinessess is created in the memory and memoizedFetchBusinesses variable is created which also references same function in the memory.

after the first rerender, a function referred as fetchBusinessess will be created again but this time in a different memory location Since we have [ ] in useCallback, memoizedFetchBusinesses will give you the original fetchBusinesses function in the same memory. useCallback here will you the same reference of the function which was created in the first rendering of your component.

useEffect(()=>{
    memoizedFetchBusinesses();
},[memoizedFetchBusinesses]) 

instead you could define function like this

const fetchBusinesses = useCallback(() => {
    return fetch("theURL", {method: "GET"}
    )
      .then(res => normalizeResponseErrors(res))
      .then(res => {
        return res.json();
      })
      .then(rcvdBusinesses => {
        // some stuff
      })
      .catch(err => {
        // some error handling
      });
  },[]);

then in useEffect

useEffect(() => {
    fetchBusinesses();
  }, [fetchBusinesses]);

Answer 17

You can get rid of this Es-lint warning by passing a reference to it:

Example mentioned below, however you can watch the solution on this link: https://www.youtube.com/watch?v=r4A46oBIwZk&t=8s

Warning: Line 13:8: React Hook React.useEffect has missing dependencies: 'history' and 'currentUser?.role'. Either include them or remove the dependency array react-hooks/exhaustive-deps

React.useEffect(() => {
    if (currentUser?.role !== "Student") {
        return history.push("/")
    }
}, [])

Resolution: Step 1: Move business logic it to separate const.

Now the warning is: React Hook React.useEffect has a missing dependency: 'roleChecking'.

const roleChecking = () =>{
   if (currentUser?.role !== "Student") {
        return history.push("/")
    }
}

React.useEffect(() => {
    roleChecking()
}, [])

Last step is to create a reference to the function:

  const roleRef = React.useRef();

  const roleChecking = () => {
    if (currentUser?.role !== "Student") {
      return history.push("/");
    }
  };
  roleRef.current = roleChecking;

  React.useEffect(() => {
   return roleRef.current();
  }, [currentUser?.role]);

Answer 18

It seems the fetchBusinesses function declared in the component. It means in every render it declares new function which triggers the hook.

There are 2 approaches to fix the issue.

1. Move the fetchBusinesses function declaration out of component.

2. Wrap the fetchBusinesses function with useCallback hook.

First option is preferable.

Answer 19

Search for the keywords to learn more about each warning. To ignore, add // eslint-disable-next-line to the line before.

For Example: The function used in useEffect is causing warning

useEffect(() => {
  handleConnectWallet();
}, []);

To ignore the warning we simply add "// eslint-disable-next-line" before the warning line i.e.

useEffect(() => {
  handleConnectWallet();
  // eslint-disable-next-line
}, []);

Answer 20

Just pass the function as the argument in the array of useEffect...

useEffect(() => {
   functionName()
}, [functionName])

Answer 21

using UseEffect fetchBusinesses calling function declare in useEffect() by declaring a const variable after that calling the name of the function,

useEffect(()=>{
const fetchBusinesses=()=>{
   console.log(useeffect fetchbussinesses functions)
}
 fetchBusinesses();
},[declare the variable used in useeffect hooks ])

Answer 22

To disable this warning in your project

add this "react-hooks/exhaustive-deps": "off" to .eslintrc.js file

Answer 23

You are making use of useEffect and when you do that, very frequently you want to make use of some variables that are used as props or state inside your component.

There is a rule built into eslint that wants you to reference any different prop or piece of state inside of the useEffect dependency array. That's the array that controls when useEffect gets executed. That rule wants to see it listed inside that array which decides when to re-run the useEffect function.

So you would need to add in [fetchBusinesses] and the warning should be gone.

Now, why does that rule wants us to put that in there?

There are some scenarios where making use of useEffect and not properly listing out all the pieces of state and props inside the array can lead to weird and hard to debug problems.

So this rule is to help avoid those hard to understand problems that can come up with useEffect.

Now, arbitrarily adding to that array can lead to bugs as well. So either way you are running into bugs you have to solve. According to your comments that seemed to solve it for you, but I would have wanted to investigate further to see if you by any chance got a second GET request in your Network tab in Chrome after adding in the fetchBusinesses function to your useEffect array.