简单的ReactJS Javascript输入不起作用

Question

I am trying to learn ReactJS and how Javascript code interacts with the components in ReactJS and am not able to get a simple example to work.

Given below is my index.js file:

class JsBasic extends React.Component{
  render(){

    return(
      var hello = () => alert('hello')
      hello()
  );
}
}

ReactDOM.render(
  <JsBasic/>
  document.getElementById('root')
  );

On doing a npm start , I get the following error:

./src/index.js
Syntax error: Unexpected token (53:6)

  51 | 
  52 |     return(
> 53 |       var hello = () => alert('hello')
     |       ^
  54 |       hello()
  55 |   );
  56 | }

Any help greatly appreciated.

Answer 1

You can't put variables inside return, try this instead:

class JsBasic extends React.Component{
  render(){
    var hello = () => alert('hello')
    return(hello());
  }
}

ReactDOM.render(
  <JsBasic/>
  document.getElementById('root')
  );

Answer 2

class JsBasic extends React.Component{
hello = () => {alert('hello')}
 render(){
  return(
   this.hello()
  );
 }
}

Example click here