React useMergeState Hook

Introduction

In this lab, we will explore the useMergeState hook in React. This hook allows us to create a stateful value and a function to update it by merging the new state provided. We will learn how to use this hook to simplify state management and make our code more efficient.

React useMergeState Hook

index.html and script.js have already been provided in the VM. In general, you only need to add code to script.js and style.css.

To create a stateful value and a function to update it by merging the new state provided, use the useState() hook to create a state variable and initialize it to initialState. Create a function that will update the state variable by merging the new state provided with the existing one. If the new state is a function, call it with the previous state as the argument and use the result. If no argument is provided, the state variable will be initialized with an empty object ({}). The following code demonstrates how to implement this using the useMergeState custom hook:

const useMergeState = (initialState = {}) => {
  const [value, setValue] = React.useState(initialState);

  const mergeState = (newState) => {
    if (typeof newState === "function") {
      newState = newState(value);
    }
    setValue({ ...value, ...newState });
  };

  return [value, mergeState];
};

Here is an example usage of the useMergeState hook in a component named MyApp:

const MyApp = () => {
  const [data, setData] = useMergeState({ name: "John", age: 20 });

  return (
    <>
      <input
        value={data.name}
        onChange={(e) => setData({ name: e.target.value })}
      />
      <button onClick={() => setData(({ age }) => ({ age: age - 1 }))}>
        -
      </button>
      {data.age}
      <button onClick={() => setData(({ age }) => ({ age: age + 1 }))}>
        +
      </button>
    </>
  );
};

ReactDOM.createRoot(document.getElementById("root")).render(<MyApp />);

Please click on 'Go Live' in the bottom right corner to run the web service on port 8080. Then, you can refresh the Web 8080 Tab to preview the web page.

Summary

Congratulations! You have completed the React useMergeState Hook lab. You can practice more labs in LabEx to improve your skills.