写入节点.js中的 CSV

您可以使用 fs （https://nodejs.org/api/fs.html#fs_fs_writefile_file_data_options_callback）：

var dataToWrite;
var fs = require('fs');
fs.writeFile('form-tracking/formList.csv', dataToWrite, 'utf8', function (err) {
  if (err) {
    console.log('Some error occured - file either not saved or corrupted file saved.');
  } else{
    console.log('It''s saved!');
  }
});

node-csv-parser （ npm install csv ） 的文档特别指出它可以与流一起使用（参见 fromStream ， toStream ）。因此，使用标准输出不是硬编码的。

当您npm search csv时，还会出现其他几个CSV解析器 - 您可能也想查看它们。

这是一个使用 csv-stringify 使用 fs.writeFile 将适合内存的数据集写入 csv 文件的简单示例。

import stringify from 'csv-stringify';
import fs from 'fs';
let data = [];
let columns = {
  id: 'id',
  name: 'Name'
};
for (var i = 0; i < 10; i++) {
  data.push([i, 'Name ' + i]);
}
stringify(data, { header: true, columns: columns }, (err, output) => {
  if (err) throw err;
  fs.writeFile('my.csv', output, (err) => {
    if (err) throw err;
    console.log('my.csv saved.');
  });
});

按照你所说的那样使用循环，你可以用 Node fs 做这样的事情：

let fs = require("fs")
let writeStream = fs.createWriteStream('/path/filename.csv')
someArrayOfObjects.forEach((someObject, index) => {     
    let newLine = []
    newLine.push(someObject.stringPropertyOne)
    newLine.push(someObject.stringPropertyTwo)
    ....
    writeStream.write(newLine.join(',')+ ''n', () => {
        // a line was written to stream
    })
})
writeStream.end()
writeStream.on('finish', () => {
    console.log('finish write stream, moving along')
}).on('error', (err) => {
    console.log(err)
})

如果您不想使用 fs 以外的任何库，您可以手动执行此操作。

let fileString = ""
let separator = ","
let fileType = "csv"
let file = `fileExample.${fileType}`
Object.keys(jsonObject[0]).forEach(value=>fileString += `${value}${separator}`)
    fileString = fileString.slice(0, -1)
    fileString += "'n"
    jsonObject.forEach(transaction=>{
        Object.values(transaction).forEach(value=>fileString += `${value}${separator}`)
        fileString = fileString.slice(0, -1)
        fileString += "'n"
    })
fs.writeFileSync(file, fileString, 'utf8')

编写CSV非常简单，无需库即可完成。

import { writeFile } from 'fs/promises';
// you can use just fs module too
// Let's say you want to print a list of users to a CSV
const users = [
  { id: 1, name: 'John Doe0', age: 21 },
  { id: 2, name: 'John Doe1', age: 22 },
  { id: 3, name: 'John Doe2', age: 23 }
];
// CSV is formatted in the following format 
/*
  column1, column2, column3
  value1, value2, value3
  value1, value2, value
*/
// which we can do easily by
const dataCSV = users.reduce((acc, user) => {
    acc += `${user.id}, ${user.name}, ${user.age}'n`;
    return acc;
  }, 
  `id, name, age'n` // column names for csv
);
// finally, write csv content to a file using Node's fs module
writeFile('mycsv.csv', dataCSV, 'utf8')
  .then(() => // handle success)
  .catch((error) => // handle error)

注意：如果您的 CSV 内容中包含,，则必须对其进行转义或使用其他分隔符。如果是这种情况，我建议使用像csv-stringify这样的库。

对于那些喜欢快速csv的人：

const { writeToPath } = require('@fast-csv/format');
const path = `${__dirname}/people.csv`;
const data = [{ name: 'Stevie', id: 10 }, { name: 'Ray', id: 20 }];
const options = { headers: true, quoteColumns: true };
writeToPath(path, data, options)
        .on('error', err => console.error(err))
        .on('finish', () => console.log('Done writing.'));

**如果您不想使用 fs 以外的任何库，您可以手动执行此操作。此外，您还可以在要写入CSV文件时过滤数据**

router.get('/apiname', (req, res) => {
 const data = arrayOfObject; // you will get from somewhere
 /*
    // Modify old data (New Key Names)
    let modifiedData = data.map(({ oldKey1: newKey1, oldKey2: newKey2, ...rest }) => ({ newKey1, newKey2, ...rest }));
 */
 const path = './test'
 writeToFile(path, data, (result) => {
     // get the result from callback and process
     console.log(result) // success or error
   });
});
writeToFile = (path, data, callback) => {
    fs.writeFile(path, JSON.stringify(data, null, 2), (err) => { // JSON.stringify(data, null, 2) help you to write the data line by line
            if (!err) {
                callback('success');
                // successfull
            }
            else {
                 callback('error');
               // some error (catch this error)
            }
        });
}

这是在 nest js 中对我有用的代码

import { Parser } from "json2csv";
 const csv = require('csvtojson');
      const csvFilePath = process.cwd() + '/' + file.path;
      let csv data  = await csv().fromFile(csvFilePath); /// read data from csv into an array of json 
          

/// * from here how to write data into csv *

          data.push({
                label: value,
                .......
          })                 
        }
        const fields = [
         'field1','field2', ... 
        ]
        
        const parser = new Parser({ fields, header:false }); /// if dont want header else remove header: false
        const csv = parser.parse(data);
        appendFileSync('./filename.csv',`${csv}'n`); // remove /n if you dont want new line at the end