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  useEffect(() => {
    if (steps.step2 && !requestKey) {
      const timeoutId = setTimeout(() => startProcess(), 500)
      return () => clearTimeout(timeoutId)
  }, [steps, requestKey, startProcess])
eslint complains me  error  Expected to return a value at the end of arrow function  consistent-return
for return () => clearTimeout(timeoutId)
Because when i comment this an error disappears.
// return () => { clearTimeout(timeoutId); }
How to solve this, any ideas?
If you're returning in at least one branch, you need to always return a value to follow the rule. It doesn't have to be a function, it just has to be something other than the standalone statement return. This works too:
  useEffect(() => {
    if (steps.step2 && !requestKey) {
      const timeoutId = setTimeout(() => startProcess(), 500)
      return () => clearTimeout(timeoutId)
    return undefined;
  }, [steps, requestKey, startProcess])
Also note that setTimeout(() => startProcess(), 500) simplifies to setTimeout(startProcess, 500).
                ESLing should learn that a single return; in an untyped function will always return undefined which means that return; is exactly the same thing as return undefined;, both will return undefined.
– Christos Lytras
                Apr 4, 2021 at 21:33
When i add this return () => {} at the end of useEffect(() => {...})
Now eslint doesn't complains about this.
  useEffect(() => {
    if (steps.step2 && !requestKey) {
      const timeoutId = setTimeout(() => startProcess(), 500)
      return () => clearTimeout(timeoutId)
    + return () => {}
  }, [steps, requestKey, startProcess])
                Returning an empty function is unnecessary to resolve this linter error. As @CertainPerformance's answer states, you can return undefined instead.
– timgcarlson
                Jun 24, 2022 at 16:48
        
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