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I'm writing a NodeJS app using JS and fs to manage the filesystem. I'm using compile and resolve-to-string to replace template strings with config values. The result of that ends up in content. I'm on a Mac. Not sure that matters.

Then I have this:

  try {
    fs.writeFileSync(destFileName, content, 'utf8')
    fs.appendFileSync(destFileName, '\r', 'utf8')
  } catch (e) {
    console.error(e)
  }

content is a string and is written out to the .json file just fine. I can't for the life of me figure out how to add a newline to the end of the file. I've tried as many combos of \r and \n as I can think of. I've tried a few different fs file options. I've tried with and without utf8. I assume it's something super small and silly but I can't see it. :(

Following aRvi's comment, I tried adding several \n's to content and then console.loging it. All the extra newlines show up just fine in the console. Then I tried writing content to a .txt file. Extra newlines show up fine there too. Then I tried renaming .txt to a .json file and the newlines disappeared. Must be something to do with file format/extension.

Jason Anderson
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  • https://stackoverflow.com/questions/10384340/how-to-append-to-new-line-in-node-js – user2258152 Sep 25 '20 at 17:08
  • My initial Google search landed me there first. I've tried several combinations of `\r` and `\n` without any luck. – Jason Anderson Sep 25 '20 at 17:10
  • `fs.writeFileSync(destFileName, content + "\n", 'utf8')` check if that works for you – aRvi Sep 25 '20 at 17:12
  • Tried that too. Also doesn't work. I've added more details to the question RE to this. – Jason Anderson Sep 25 '20 at 17:19
  • When I replaced "\r" with "\n" in your code, it worked fine on my mac. How do you know the newline disappears in the .json file? How are you opening/viewing the .json file? There's a chance your text editor is modifying the file when you open/save it. – Elliot Plant Feb 02 '22 at 16:57
  • Have you tried viewing your modified file in different editors? Do they all behave the same? – Dinkar Jain Jun 12 '22 at 12:16

3 Answers3

1

The following works for me. You'll need two newline characters if you're looking to actually have a blank line at at the bottom. One to end the current line, and the second to create the empty line below.

const fs = require("fs");
const { EOL } = require("os");

const destFileName = "./new-file.json";
const content = "hello world";

try {
  fs.writeFileSync(destFileName, content, "utf8");
  fs.appendFileSync(destFileName, EOL, "utf8");
  fs.appendFileSync(destFileName, EOL, "utf8");
} catch (e) {
  console.error(e);
}

$ cat new-file.js
hello world
Matt
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0

This works for me.

 fs.writeFileSync(destFileName, content + '\n', 'utf8')

It could be that your IDE/editor automatically removes any extra whitespace after the last character in the JSON file.

Isaac Jandalala
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0

Ran node code in node v16.15.1

Below I wrote some code that anyone can run to see that the console will log that three newLine characters in a row were there after the file was written to. This is most likely an IDE issue for most people because the default JSON formatter on Auto Save will remove any extra whitespace and new lines. I took the liberty of adding the .vscode/settings.json config to override this default functionality for your workspace.

const fs = require("fs");
    const content = `{
      "demokey": {
        "demokey2": "demovalue2",
        "demokey2": "demovalue2"
      }
    }
    `;
    try {
      fs.writeFileSync("./demo.json", content, "utf8");
      fs.appendFileSync("./demo.json", "\n\n\n", "utf8");
      const text = fs.readFileSync("./demo.json");
      const hasThreeLinesInARow = /\n\n\n/.test(text.toString());
      console.log(hasThreeLinesInARow);
    } catch (e) {
      console.error(e);
    }

vs code config - save to project/.vscode/settings.json

{
    "json.format.enable": false,
    "json.validate.enable": false
}
Andrew Williams
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