Copying an array from React Hook

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I'm using the useState hook to populate items in an array.

const [meals, setMeals] = useState([]);
useEffect(async () =>{
    const mealsData = await fetchMeals(localStorage.getItem('user_id'));
    console.log(mealsData);// Array(3)
    setMeals([...meals, mealsData]);
    console.log(meals);//[]
 }, []);

The array doesn't get copies in my setMeals method, what am I doing wrong here?

This is because

setMeals([...meals, mealsData]);

is an asynchronous call and you are logging the meals before being sure the state actually updated

console.log(meals);

You should call and check your console.log() function in another useEffect() call which runs on every state change and assures that the state actually changed

useEffect(() => {
    console.log(meals);
 }, [meals]);

[meals] passed as the second argument will let this useEffect() run every time meals (actually) update.

How to Add to an Array in React State using Hooks, helps when copying and combining arrays, so it can also be used to add an item to an array in React state. [searches, query] to append an item� Both of the options you provided are the same. Both of them will still point to the same object in memory and have the same array values. You should treat the state object as immutable as you said, however you need to re-create the array so its pointing to a new object, set the new item, then reset the state.

the update is asynchronous, the new value is not available immediately as you're expecting. You can find an in-depth explanation here: useState set method not reflecting change immediately

react hook copy previous array state Code Example, Get code examples like "react hook copy previous array state" instantly right from your google search results with the Grepper Chrome� W hen React state is an array, it is not obvious how to add items to the array, such as when trying to update state using React Hooks. This question might come up when state is a list of items.

UseEffect cannot be async you should wrap it in an async function

function useMeals() {
   const [meals, setMeals] = useState([]);
    useEffect(() => {
      async function setFetchedMeals() {
        const mealsData = await fetchMeals(localStorage.getItem('user_id'));
        setMeals([...meals, mealsData]);
      }
      setFetchedMeals();
    }, []); // letting the dependency array empty will run the effect only once

  console.log(meals)
  return meals;
}

4 Examples of the useState Hook, There are a bunch of React hooks, but useState is the workhorse of the ES6 spread operator to copy the existing items into the new array,� Example 2: Filter an Array of Objects by Value in React. Let’s explore how to filter an array of objects in React, based on a value inside of those objects. It’s similar to what we did previously with the array of strings, just with an extra step. Our array of names has expanded, and so I renamed the array to be named people. It now looks

You are actually not doing anything wrong, state updates are not synchronous, so logging meals immediately after updating it will not show the updated value

Use an effect for the meals array to detect when it has actually changed...

useEffect(() => {
    console.log(meals);
}, [meals]);

React Hooks Tutorial - 5 - useState with array, Support - https://www.paypal.me/Codevolution Facebook - https://www.facebook. com Duration: 5:55 Posted: 20 May 2019 With the Form component injecting react-hook-form's props into the child component, you can easily create and compose complex forms in your app. Field Arrays. This is one of the best features about React Hook Form: instead of importing components (like other libraries) to achieve this functionality, you can leverage your existing HTML markup.

React Hooks - useState - DEV, The useState hook allows us to make our function components stateful. items. push({item3}) // Instead, make a copy of the array then add your� That's only one way of providing a fallback for an array being null. As alternative, you can also use React's conditional rendering for it.. The second question, which asks how to push an empty array in React state, involves manipulating the state with this.setState().

The React Hooks Guide, Let's briefly take a look at some code that demonstrates the reduce method from JavaScript's Array.prototype . Copy Code const votesByDistrict = [250, 515� I have an array of objects. I need to add a function to remove an object from my array without using the "this" keyword. I tried using updateList(list.slice(list.indexOf(e.target.name, 1))). This removes everything but the last item in the array and I'm not certain why.

Invalid Hook Call Warning – React, Hooks can only be called inside the body of a function component. There are three You might have more than one copy of React in the same app. Let's look at� As pointed in the react docs: Never mutate this.state directly, as calling setState() afterwards may replace the mutation you made. Treat this.state as if it were immutable. In this case, you can [1] use slice() to get a new copy of the Array, [2] manipulate the copy, and, then, [3] setState with the new Array. It's a good practice.

Comments
  • What's the solution?
  • I edited and added the solution. Let me know if that works...