Passing an empty array as the second argument to useEffect makes it only run on mount and unmount, thus stopping any infinite loops. useEffect(() => { setIngredients({}); }, []); This was clarified to me in the blog post on React hooks at https://www.robinwieruch.de/react-hooks/
For your scenario (where you cannot keep creating new callbacks and passing them to your 3rd party library), you can use useRef to keep a mutable object with the current state. Like so: function Card(title) { const [count, setCount] = React.useState(0) const [callbackSetup, setCallbackSetup] = React.useState(false) const stateRef = useRef(); // make stateRef always have … Read more
You can use useEffect/useLayoutEffect to achieve this: const SomeComponent = () => { const [count, setCount] = React.useState(0) React.useEffect(() => { if (count > 1) { document.title=”Threshold of over 1 reached.”; } else { document.title=”No threshold reached.”; } }, [count]); return ( <div> <p>{count}</p> <button type=”button” onClick={() => setCount(count + 1)}> Increase </button> </div> ); … Read more
Defined return () => { /*code/* } function inside useEffect runs every time useEffect runs (except first render on component mount) and on component unmount (if you don’t display component any more). This is a working way to use and clear timeouts or intervals: Sandbox example. import { useState, useEffect } from “react”; const delay … Read more
You’re calling setNumbers and passing it the array it already has. You’ve changed one of its values but it’s still the same array, and I suspect React doesn’t see any reason to re-render because state hasn’t changed; the new array is the old array. One easy way to avoid this is by spreading the array … Read more
This is possible with useState or useReducer, since useState uses useReducer internally: const [, updateState] = React.useState(); const forceUpdate = React.useCallback(() => updateState({}), []); forceUpdate isn’t intended to be used under normal circumstances, only in testing or other outstanding cases. This situation may be addressed in a more conventional way. setCount is an example of … Read more
As you cannot use hooks inside loops, here is a solution in order to make it work when the array changes over the time. I suppose the array comes from the props : const App = props => { const itemsRef = useRef([]); // you can access the elements with itemsRef.current[n] useEffect(() => { itemsRef.current … Read more
The argument passed to useState is the initial state much like setting state in constructor for a class component and isn’t used to update the state on re-render If you want to update state on prop change, make use of useEffect hook function Avatar(props) { const [user, setUser] = React.useState({…props.user}); React.useEffect(() => { setUser(props.user); }, … Read more
You could combine the loading state and data state into one state object and then you could do one setState call and there will only be one render. Note: Unlike the setState in class components, the setState returned from useState doesn’t merge objects with existing state, it replaces the object entirely. If you want to … Read more
The reason is because the callback passed into setInterval‘s closure only accesses the time variable in the first render, it doesn’t have access to the new time value in the subsequent render because the useEffect() is not invoked the second time. time always has the value of 0 within the setInterval callback. Like the setState … Read more