How can user input be added to an empty nested array using useState?

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You can use the useState hook to create an empty nested array and then add user input to it using the set method. Here's an example:

import React, { useState } from "react";

function MyComponent() {
  const [nestedArray, setNestedArray] = useState([]);

  const addInputToNestedArray = (input) => {
    setNestedArray((prevNestedArray) => [...prevNestedArray, input]);
  };

  return (
    <div>
      <input
        type="text"
        onChange={(e) => {
          addInputToNestedArray(e.target.value);
        }}
      />
      <button onClick={() => addInputToNestedArray("default value")}>
        Add default value
      </button>
      <pre>{JSON.stringify(nestedArray, null, 2)}</pre>
    </div>
  );
}

In this example, we create an empty nested array using the useState hook:

const [nestedArray, setNestedArray] = useState([]);

We then define a function called addInputToNestedArray that takes an input and adds it to the nested array using the set method. We use the spread operator (...) to create a new array that contains the previous nested array with the new input appended to the end:

const addInputToNestedArray = (input) => {
  setNestedArray((prevNestedArray) => [...prevNestedArray, input]);
};

In the render method, we create an input field that calls the addInputToNestedArray function on change. We also create a button that adds a default value to the nested array. Finally, we display the nested array using JSON.stringify.