通过FileReader Api读取文件并将其转换为json对象 [英] Read a File through FileReader Api and Convert it into json object

问题描述

我正在一个Reactjs项目上.在该项目中，我有这样的场景，例如我需要从本地读取一个csv文件并将其转换为json对象.我正在使用 csvtojson 节点程序包将csv文件转换为json对象.请参见下面的代码:

I am working on a Reactjs Project .In the project I have scenario like I need to read a csv file from local and convert it into json objects. I am using csvtojson node package for converting csv files to json objects. See the code below:

import React from 'react';
import ReactDOM from 'react-dom';

var objects;

var ReadFile = React.createClass({
    readFile:function(){
        var file = this.refs.file.files[0];
        var reader = new FileReader();
        reader.onload = function(evt){
             var resultText = evt.target.result;
             objects = this.csvToJson(resultText);
             console.log(objects);
        }.bind(this);
        var newFile = file.slice(0,5000);
        reader.readAsText(newFile); 
    },
    csvToJson:function(csvString){
        var Converter = require("csvtojson").Converter;
        var converter = new Converter({});
        converter.fromString(csvString, function(err,result){
           //When i console log the result it is working but when i return The result:
           // i am getting a undefined error
           //console.log(result);
           return result;
        });
    },
    render:function(){
      return (
         <input type="file" ref="file" onChange={this.readFile} /> 
      );
    }
});

ReactDOM.render(<ReadFile />,document.getElementById('container'));

当我从 csvToJson 文件控制台记录结果时，出现了未定义的错误.请有人指导我，我在做什么错了?

When I console log the result from the csvToJson file I am getting a undefined error. Please somebody guide me, what I am doing wrong?

推荐答案

import React, { Component } from 'react'
import { connect } from 'react-redux'
import ReactFileReader from 'react-file-reader';

export default class CsvRead extends React.Component {
  constructor(props) {
    super(props);
  }
  handleFiles = files => {
    var reader = new FileReader();
    reader.onload = function(e) {
    // Use reader.result
    var csv = reader.result;
    var lines = csv.split("\n");
    var result = [];
    var headers=lines[0].split(",");
    for(var i=1;i<lines.length;i++){
      var obj = {};
      var currentline=lines[i].split(",");
      for(var j=0;j<headers.length;j++){
        obj[headers[j]] = currentline[j];
      }
      result.push(obj);
      }  
      //return result; //JavaScript object
      result= JSON.stringify(result); //JSON
    console.log(result);
  }
  reader.readAsText(files[0]);
}

  render() {
    return (
      <ReactFileReader handleFiles={this.handleFiles} fileTypes={'.csv'}>
        <button className='btn'>Upload</button>
      </ReactFileReader>
    );
  }
}

这可以正常工作.

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