React useMap Hook

Introduction

In this lab, we will explore the useMap hook in React, which creates a stateful Map object and a set of functions to manipulate it. By using this hook, we can easily manage and update key-value pairs in our React components without having to write complex and error-prone logic. This lab will guide you through the implementation of the useMap hook and demonstrate its usage in a sample application.

React useMap 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.

• The useMap() hook creates a stateful Map object and a set of functions to manipulate it using React hooks.
• The useState() hook initializes the Map state with the initialValue.
• The useMemo() hook creates a set of non-mutating actions that manipulate the map state variable using the state setter to create a new Map every time.
• The useMap() hook returns an array containing the map state variable and the created actions.
• The MyApp component uses the useMap() hook to initialize the stateful Map object and provides buttons to add, reset, and remove items from the Map.
• The JSON.stringify() function formats the Map object into a readable JSON string.

const useMap = (initialValue) => {
  const [map, setMap] = React.useState(new Map(initialValue));

  const actions = React.useMemo(
    () => ({
      set: (key, value) =>
        setMap((prevMap) => {
          const nextMap = new Map(prevMap);
          nextMap.set(key, value);
          return nextMap;
        }),
      remove: (key) =>
        setMap((prevMap) => {
          const nextMap = new Map(prevMap);
          nextMap.delete(key);
          return nextMap;
        }),
      clear: () => setMap(new Map())
    }),
    [setMap]
  );

  return [map, actions];
};

const MyApp = () => {
  const [map, { set, remove, clear }] = useMap([["apples", 10]]);

  const handleAdd = () => set(Date.now(), new Date().toJSON());
  const handleReset = () => clear();
  const handleRemove = () => remove("apples");

  return (
    <div>
      <button
      <button
      <button disabled={!map.has("apples")}>
        Remove apples
      </button>
      <pre>{JSON.stringify(Object.fromEntries(map), null, 2)}</pre>
    </div>
  );
};

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 useMap Hook lab. You can practice more labs in LabEx to improve your skills.