自从我对JavaScript和React感到陌生以来，我确实在找出正确的语法方面遇到了问题。

这是我的问题：

_handleDrop(files)应该调用该函数，_validateXML(txt)但不会。我收到此错误Uncaught TypeError: this._validateXML is not a function，无法找出原因。回调_handleDrop(files)可以正常工作。

当我尝试这种语法_validateXML:function(txt)时，在编译时会立即出现错误。那是因为电子书吗？

import React from 'react';
import './UploadXML.scss';
import Dropzone from 'react-dropzone';
import xml2js from 'xml2js';

export default class UploadXML extends React.Component {

  constructor() {
    super();
    this._validateXML = this._validateXML.bind(this);
  }

  _validateXML(txt) {
    console.log('Received files: ', txt);
  }

  _handleDrop(files) {
    if (files.length !== 1) {
      throw new Error("Please upload a single file");
    }
    var file = files[0];

    console.log('Received files: ', file);

    this._validateXML(file);
  }

  render() {
    return (
      <div>
            <Dropzone onDrop={this._handleDrop} multiple={false}>
              <div>Try dropping some files here, or click to select files to upload.</div>
            </Dropzone>
      </div>
    );
  }
}