手写createContext

实现

API使用

import { useState, createContext, useContext } from "react";
import ReactDOM from "react-dom";
const UserContext = createContext();
function Component1() {
  const [user, setUser] = useState("Jesse Hall");
  return (
    <UserContext.Provider value={user}>
      <h1>{`Hello ${user}!`}</h1>
      <Component2 user={user} />
    </UserContext.Provider>
  );
}
function Component2() {
  return (
    <>
      <h1>Component 2</h1>
      <Component3 />
    </>
  );
}
function Component3() {
  return (
    <>
      <h1>Component 3</h1>
      <Component4 />
    </>
  );
}
function Component4() {
  return (
    <>
      <h1>Component 4</h1>
      <Component5 />
    </>
  );
}
function Component5() {
  const user = useContext(UserContext);
  return (
    <>
      <h1>Component 5</h1>
      <h2>{`Hello ${user} again!`}</h2>
    </>
  );
}
ReactDOM.render(<Component1 />, document.getElementById("root"));