我有這個(gè) React 代碼，您也可以在此處查看代碼https://stackblitz.com/edit/react-excel-to-json-parser。當(dāng)我在沒(méi)有上傳文件的情況下單擊“處理觸發(fā)器”按鈕時(shí)。該應(yīng)用程序打破了如何處理用戶必須上傳文件或禁用按鈕“處理觸發(fā)器”直到用戶上傳文件的警報(bào)錯(cuò)誤。import React, { Component } from 'react';import { Fabric } from 'office-ui-fabric-react/lib/Fabric';import { DefaultButton } from 'office-ui-fabric-react/lib/Button';import XLSX from 'xlsx';import { make_cols } from './MakeColumns';import { SheetJSFT } from './types'; class ExcelReader extends Component {  constructor(props) {    super(props);    this.state = {      file: {},      data: [],      cols: []    }    this.handleFile = this.handleFile.bind(this);    this.handleChange = this.handleChange.bind(this);  }   handleChange(e) {    const files = e.target.files;    if (files && files[0]) this.setState({ file: files[0] });  };   handleFile() {    /* Boilerplate to set up FileReader */    const reader = new FileReader();    const rABS = !!reader.readAsBinaryString;     reader.onload = (e) => {      /* Parse data */      const bstr = e.target.result;      const wb = XLSX.read(bstr, { type: rABS ? 'binary' : 'array', bookVBA : true });      /* Get first worksheet */      const wsname = wb.SheetNames[0];      const ws = wb.Sheets[wsname];      /* Convert array of arrays */      const data = XLSX.utils.sheet_to_json(ws);      /* Update state */      this.setState({ data: data, cols: make_cols(ws['!ref']) }, () => {        console.log(JSON.stringify(this.state.data, null, 2));      });     };     if (rABS) {      reader.readAsBinaryString(this.state.file);    } else {      reader.readAsArrayBuffer(this.state.file);    };  }