React Basics~useState/ count number~-JS Tutorial-php.cn

React Basics~useState/ count number~

Mary-Kate Olsen

Release： 2024-10-06 20:39:29

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The useState is a react hook that holds a state of the component.
In this case, the state is a counter.
The button increases the state of the counter. The - button decreases the counter.

・src/Example.js


import { useState } from "react";

const Example = () => {
  const [count, setCount] = useState(0);
  return (
    <>
      <CountResult title="count" count={count} />
      <CountUpdate setCount={setCount} />
    </>
  );
};
const CountResult = ({ title, count }) => (
  <h3>
    {title} : {count}
  </h3>
);

const CountUpdate = ({ setCount }) => {
  const countUp = () => {
    setCount((prev) => prev + 1);
  };
  const countDown = () => {
    setCount((prev) => prev - 1);
  };
  return (
    <>
      <button onClick={countUp}>+</button>
      <button onClick={countDown}>-</button>
    </>
  );
};

export default Example;

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・Here is the action of countup.

React Basics~useState/ count number~

・Here is the action of countdown.

React Basics~useState/ count number~

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