删除使用 join() 处理的数组中的值后，如何更新我的 state？

Question

I have an array called selectedOption that looks like this:

[
   "Fantasy",
    "Mystery",
    "Romance",
   "Scifi"
];

Using a multi-select input,

I can choose multiple options, (ie. Romance, Mystery). Then save these in a state called query

When I log selectedOption in the browser terminal and copy it, it looks like this

[
    [
        "Mystery",
        "Romance"
    ]
]

Problem

As mentioned, I need to get the string(s) and save them in query . Below is how I check if the array has stuff in it, and if it does, I use join() to get the string values and then I save that into 'query' (This data in query is used for a query search)

const [selectedOption, setSelectedOption] = useState([]);
    const [query, setQuery] = useState();

    //selecting an option

    const handleTypeSelect = (e) => {
        const copy = [...selectedOption];
        copy.push(e);
        setSelectedOption(copy);

    //to zone in on what I need, I have to get the first array value.
        console.log(selectedOption[0]);

        //only perform join() if the array has stuff in it.

        if(!selectedOption.length){
        } else {
            let joinedArr = selectedOption[0].join(", ");

            //save the strings into my query state
            setQuery(joinedArr)
            console.log(query)
        }
    };

Results Here is my query state, exactly what I want:

Problem Everything kinda works to this point. The issue I have is that, when I delete 'Romance' for example, it's not reflected in my query state. Below is the code to remove one select option. How do I write this code so that when I delete an option, it's reflected in my query state , do I need to make it into an object again?

    const handleTypeRemove = (e) => {
        const copy = [...selectedOption];
        let index = copy.indexOf(e);
        copy.splice(index, 1);
        setSelectedOption(copy);
    };

When I delete something ie.

It does not delete it from query - here is the log fired up after calling handleTypeRemove

Your help is greatly appreciated, assume you are explaining to a child.

Answer 1

The copied variable does not change the state, you'll have to also update the query with setQuery

    const handleTypeRemove = (e) => {
        const copy = [...selectedOption];
        let index = copy.indexOf(e);
        copy.splice(index, 1);
        setSelectedOption(copy);
        setQuery(copy.join(', '));
    };

Instead of having two sets of logic doing the same thing, instead you can use React useEffect .

Like so

  const handleTypeSelect = (e) => {
    const copy = [...selectedOption];
    copy.push(e);
    setSelectedOption(copy);
  };
  const handleTypeRemove = (e) => {
    const copy = [...selectedOption];
    const index = copy.indexOf(e);
    copy.splice(index, 1);
    setSelectedOption(copy);
  };
  useEffect(() => {
    if (!selectedOption.length) {
    } else {
      const joinedArr = selectedOption[0].join(", ");

      //save the strings into my query state
      setQuery(joinedArr);
      console.log(query);
    }
    // this means this code inside this block runs everytime selectedOption changes
  }, [selectedOption]);