Unexpected Token after const

问题

I am getting an unexpected token error in React when I try to specify a constant, and I cannot seem to figure out why.

My code is pretty simple, and I have followed the react-bootstrap examples here almost exactly.

My code is as follows:

import { Component, PropTypes } from 'react';

var rbs = require('react-bootstrap'),
Panel = rbs.Panel;

export default class ResumeSection extends Component {
  constructor(...args) {
    super(...args);
    this.state = {
      open: true
    };
  }

  const title = (
    <h3>Panel title</h3>
  );

  render() {
    return (
      <Panel collapsible expanded={this.state.open}>
        <p>Body</p>
      </Panel>
    );
  }
}

The error occurs on title directly after const and just says SyntaxError: Unexpected Token

回答1:

You can't define a const in the class body like that; it should be moved into a method.

render() {
  const title = (
    <h3>Panel title</h3>
  );
  // ...
}

回答2:

Apparently, this is called "Public Class Field Syntax" and is already available in babel as the plugin, babel-plugin-transform-class-properties. I have not tried it as yet though.

Additional reference is reactjs.org events guide

来源：https://stackoverflow.com/questions/34801480/unexpected-token-after-const