others-Why my onclick function is not working inside a react component?

1. Purpose

In this post, I would demo how to solve the onClick function not working when using react to write a component.

2. Environment

  • npm and node version:
➜  ~ npm version
{
  npm: '8.1.2',
  node: '17.1.0',
  v8: '9.5.172.25-node.13',
  uv: '1.42.0',
  zlib: '1.2.11',
  brotli: '1.0.9',
  ares: '1.18.1',
  modules: '102',
  nghttp2: '1.45.1',
  napi: '8',
  llhttp: '6.0.4',
  openssl: '3.0.0+quic',
  cldr: '39.0',
  icu: '69.1',
  tz: '2021a',
  unicode: '13.0',
  ngtcp2: '0.1.0-DEV',
  nghttp3: '0.1.0-DEV'
}

3. The code and solution

3.1 The code that causing problem

I am writing a very simple react component, which is just a square button, it would print on click 222 when user click it.

class Square extends React.Component {
  onClickMe() {
    console.log("on click 222");
  }
  render() {
    return (
      <button className="square" onClick={this.onClickMe()}>
        {this.props.value}
      </button>
    );
  }
}

But when I run the code, I got this:

image-20211128213045086

You can see that the code is not working as expected, it just show 9 on click 222 after startup(Because we have 9 squares), but we haven’t click any of the square yet. When I click a square, nothing happens, onClick is not working. Why?

3.2 The solution

According to this document, we should pass a function reference instead of passing the function itself to a component in the react applications.

class Square extends React.Component {
  onClickMe() {
    console.log("on click 222");
  }
  render() {
    return (
      <button className="square" onClick={this.onClickMe}>
        {this.props.value}
      </button>
    );
  }
}

The key point is:

<button className="square" onClick={this.onClickMe}>

Notice we have removed the function call () , just pass this.onClickMe, which is a function pointer or reference.

Re-run the app, we got this:

image-20211128110725486

You can see that there is no 9 logs any more, when we click any of the square, the log is showing.

4. Summary

In this post, I demonstrated how to solve the onClick not working problem when using react component, To write a component with function calls on events, we should notice that we should pass the reference not the function itself . That’s it, thanks for your reading.

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