为什么要在构造函数之外设置React组件的状态?

所以我刚刚从React框架下载了源代码，我在终端中得到这个错误:

  ERROR in ./src/components/TextEditor.js
  Module build failed: SyntaxError: Unexpected token (24:8)
  22 | 
  23 |   // Set the initial state when the app is first constructed.
> 24 |   state = {
     |         ^
  25 |     state: initialState
  26 |   }
  27 | 

我的问题是，为什么人们这样设置一个React组件的状态?如果对某些人有误差，有什么好处呢?此外，是否有一个Babel预设或插件，我可以得到防止这个错误?

这是我通常设置组件状态的方式，从我所看到的来看，这是常规的:

constructor() {
  super();
  this.state = {
    state: initialState
  };
}

为记录，这是整个文档:

// Import React!
import React from 'react'
import {Editor, Raw} from 'slate'
const initialState = Raw.deserialize({
  nodes: [
    {
      kind: 'block',
      type: 'paragraph',
      nodes: [
        {
          kind: 'text',
          text: 'A line of text in a paragraph.'
        }
      ]
    }
  ]
}, { terse: true })
// Define our app...
export default class TextEditor extends React.Component {
  // Set the initial state when the app is first constructed.
  state = {
    state: initialState
  }
  // On change, update the app's React state with the new editor state.
  render() {
    return (
      <Editor
        state={this.state.state}
        onChange={state => this.setState({ state })}
      />
    )
  }
}