How can I append one line to the last end in out.csv?

[luckymore]

This will overwrite the existing file data

const createCsvWriter = require('csv-writer').createObjectCsvWriter;  
const csvWriter = createCsvWriter({  
  path: 'out.csv',
  header: [
    {id: 'name', title: 'Name'},
    {id: 'surname', title: 'Surname'},
    {id: 'age', title: 'Age'},
    {id: 'gender', title: 'Gender'},
  ]
});

const data = [  
  {
    name: 'John',
    surname: 'Snow',
    age: 26,
    gender: 'M'
  }, {
    name: 'Clair',
    surname: 'White',
    age: 33,
    gender: 'F',
  }, {
    name: 'Fancy',
    surname: 'Brown',
    age: 78,
    gender: 'F'
  }
];

csvWriter  
  .writeRecords(data)
  .then(()=> console.log('The CSV file was written successfully'));

[ryu1kn]

Hi @luckymore , you can specify append: true when you create csvWriter.

https://github.com/ryu1kn/csv-writer#parameters

[luckymore]

Thank god!!! you have created the append option! module fast-csv don't have this...

[luckymore]

@ryu1kn I have another question. how big is too big for the csv file handling with nodejs

[ryu1kn]

I assume you're passing huge amount of records to a single writeRecords call. It depends on your memory size.

If you split it into multiple writeRecords calls, you wouldn't have the memory problem. Or you can create your transform stream, see this comment.

[luckymore]

@ryu1kn oh~ stream and pipe can hold everything. When set append: true, will need read the whole file before write file. I want know the theory.

[ryu1kn]

You use append: true if the csv file you want to write to already exist and have records in it.

Once you created csvWriter, this is tied to your csv file; so you just call csvWriter.writeRecords whenever you want to add more records into the csv file. If you're getting data by chunks, you would call writeRecords multiple times I guess.

[luckymore]

yeah, you know what I think

[kanishkamehta801]

but when append is set to true, headers are not showing

[ryu1kn]

@kanishkamehta801 You use append: true when the file you want to write CSV data to already exists (so headers are already in the file).

If you're create a new file, then you don't use append: true. CSV Writer will create a file with a header record.