Write CSV Files In NodeJS (Very Simple Examples)

Welcome to a quick tutorial and examples of how to write CSV files in NodeJS. Need to generate a CSV report or save some log entries in CSV format?

Yes, it’s that simple, but read on for more examples!

 

 

TABLE OF CONTENTS

 

 

EXAMPLE CODE DOWNLOAD

Source code on GitHub Gist

Just click on “download zip” or do a git clone. I have released it under the MIT license, so feel free to build on top of it or use it in your own project.

 

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1) WRITE ARRAY TO CSV FILE

// (A) LOAD REQUIRED MODULES
// https://www.npmjs.com/package/csv-stringify
const fs = require("fs"),
      csv = require("csv-stringify");

// (B) DATA TO WRITE
var data = [
  ["Apple", "Banana"],
  ["Cherry", "Durian"],
  ["Elderberry", "Fig"]
];

// (C) CREATE CSV FILE
csv.stringify(data, (err, output) => {
  fs.writeFileSync("demoA.csv", output);
  console.log("OK");
});

This is pretty much the “full version” of the introduction snippet. CSV (comma-separated values) is not a mystery, it is pretty much just a long string of data.

• Columns are separated with commas ,
• Rows are separated with line breaks \r\n
• Entries with commas are enclosed in a pair of double quotes "Foo,Bar"

That’s all – The CSV stringify module does this “array to CSV string” for you automatically. All we need to do is save the CSV string into a file. The end.

 

2) WRITE OBJECT TO CSV FILE

// (A) LOAD REQUIRED MODULES
// https://www.npmjs.com/package/csv-stringify
const fs = require("fs"),
      csv = require("csv-stringify");

// (B) DATA ARRAY
var data = [
  { ani: "Doge", desc: "Goodest Boy" },
  { ani: "Cate", desc: "Evil" },
  { ani: "Birb", desc: "Happy Wings" }
];

// (C) CREATE CSV FILE
csv.stringify(data, {
  header : true,
  columns : { ani : "Animal", desc : "Description" }
}, (err, output) => {
  fs.writeFileSync("demoB.csv", output);
  console.log("OK");
});

Not much of a difference in this example. If the first row is the header, just specify header : true and the columns columns : { ani : "Animal", desc : "Description" }. CSV stringify will do the rest of the “conversion” once again – We only need to save the output.

 

 

3) WRITE ROW BY ROW

// (A) LOAD REQUIRED MODULES
// https://www.npmjs.com/package/csv-stringify
const fs = require("fs"),
      csv = require("csv-stringify");

// (B) DATA ARRAY
var data = [
  ["Alpha", "Beta"],
  ["Charlie", "Delta"],
  ["Echo", "Foxtrot"]
];
 
// (C) WRITE TO FILE ROW BY ROW
for (row of data) {
  console.log(row);
  csv.stringify([row], (err, output) => {
    console.log(row);
    fs.appendFileSync("demoC.csv", output);
  });
}

If you are dealing with a large dataset, it is not recommended to dump a massive array into CSV stringify. For example, exporting data from a database into a CSV file. In this case, it is best to write row by row instead.

P.S. If you need an actual example, check out the “Node import/export MYSQL to CSV” link below.

 

 

 

LINKS & REFERENCES

• How to write files in NodeJS – Code Boxx
• CSV Stringify – NPMJS
• Import Export CSV In NodeJS MySQL – Code Boxx