Question

基本上，当我在node.js上运行csvtojson模块时没有任何代码，它完美地工作。但是一旦我将它放入函数中，即使我的文件路径仍然存在，它也只是未定义。

Js代码：

var Converter = require("csvtojson").Converter;
// create a new converter object
var converter = new Converter({});
var MongoClient = require('mongodb').MongoClient;
var url = 'mongodb://localhost:27017/myproject';

// call the fromFile function which takes in the path to your 
// csv file as well as a callback function

var  woops;

var createNewEntries = function(db, woops, callback) {

converter.fromFile("./NTA-SAM-Inventory-List-Security-Management-
                   New_2017.csv",function(err, result){
    // if an error has occured then handle it
    if(err){
        console.log("An Error Has Occured");
        console.log(err);  
    } 
    // the result of the conversion
        console.log(result);
        console.log('ohhhhh');
        woops=result;
});
console.log(woops);
};
    MongoClient.connect(url, function(err, db) {
        if(err) {
            console.log(err);
        }
        setTimeout(function(){
        createNewEntries(db, woops, function(){
            if(err)
                throw err;
            else{
                console.log(woops);
            }
            db.close();
        });
        },2000);

    });

这只是测试它是否在函数内部转换而只是显示

undefined [] ohhhhh 在函数中根本没有转换。那究竟是什么我做错了。在右边，它应该在调用函数后进行转换。是否与我在函数之前执行的代码有关？我已经放了setTimeout只是为了给它一些时间这样做我认为它不应该与我的代码顺序有关。提前谢谢！

Answer 1

根据你的输出，

undefined
[]
ohhhhh

var  woops;

var createNewEntries = function(db, woops, callback) {

converter.fromFile("./NTA-SAM-Inventory-List-Security-Management-
                   New_2017.csv",function(err, result){
    // if an error has occured then handle it
    if(err){
        console.log("An Error Has Occured");
        console.log(err);  
    } 
    // the result of the conversion
        console.log(result);        // This is getting printed second
        console.log('ohhhhh');      // This is getting printed third
        woops=result;
});
console.log(woops);                 // This is getting printed first
};
    MongoClient.connect(url, function(err, db) {
        if(err) {
            console.log(err);
        }
        setTimeout(function(){
        createNewEntries(db, woops, function(){
            if(err)
                throw err;
            else{
                console.log(woops); // This is useless!
            }
            db.close();
        });
        },2000);

    });

您可以清楚地看到这一点，因为woops变量刚刚声明，因此它必须具有undefined值。而ohhhhh之前的内容必须是结果变量。

现在，这肯定意味着至少woops变量在ohhhh之后没有被打印，或者更确切地说，createNewEntries正在执行或者在{{1}之后返回结果正在执行，这意味着你的setTimeout（）的时间不够。

为什么你甚至使用console.log(woops)并在你甚至不使用它时传递一个函数？改为使用它 -

callback

Answer 2

您应该尝试下面的文件名代码：

__dirname + "/NTA-SAM-Inventory-List-Security-Management-
                       New_2017.csv"

替换converter.fromFile()的代码，现在您的代码就是这样：

    converter.fromFile(__dirname + "/NTA-SAM-Inventory-List-Security-Management-
                               New_2017.csv" ,function(err, result){
        // if an error has occured then handle it
        if(err){
            console.log("An Error Has Occured");
            console.log(err);  
        } 
        // the result of the conversion
            console.log(result);
            console.log('ohhhhh');
            woops=result;
 MongoClient.connect(url, function(err, db) {
        if(err) {
            console.log(err);
        }
        setTimeout(function(){
        createNewEntries(db, woops, function(){
            if(err)
                throw err;
            else{
                console.log(woops);
            }
            db.close();
        });
        },2000);

    });

    });

希望它对你有用。

如果以上代码不是wouking，请尝试使用fast-csv模块下面的代码：

var fcsv = require('fast-csv');
var fs = require('fs');

/**
 * Get the records from csv
 */

var writeZipCodes = function () {
var stream = fs.createReadStream(__dirname + "/NTA-SAM-Inventory-List-Security-Management-New_2017.csv");

fcsv
  .fromStream(stream, { headers: true }) // headers for columns
  .on("data", function (data) {
          console.log(data);
          var woops=data;
          MongoClient.connect(url, function(err, db) {
            if(err) {
                console.log(err);
            }
            setTimeout(function(){
            createNewEntries(db, woops, function(){
                if(err)
                    throw err;
                else{
                    console.log(woops); 
                }
                db.close();
            });
            },2000);

        });
})
  .on("end", function () {
         console.log("done");
});
}

 writeZipCodes();

csvtojson转换器忽略我的文件名，只是放置undefined

2 个答案: