Node.js - save number to file

In this article, we would like to show you how to write line to the file in Node.js.

Quick solution:

const fs = require('fs');

const number = 123;
const data = number.toString();  // convert the number to string, so you can write it to file

fs.writeFile('./example.txt', data, (error) => {
  if (error) {
    console.error(error);
    return;
  }
});

Note:

This solution replaces the example.txt file contents if it already exists.

Additional arguments - flags

In this section, we present how to modify the quick solution from previous section by specifying an additional argument (flag) in fs.writeFile().

Practical example:

const fs = require('fs');

const number = 123;
const data = number.toString();

fs.writeFile('./example.txt', data, { flag: 'a+' }, (error) => {
  if (error) {
    console.error(error);
    return;
  }
});

Note:

Now when you run the program, the data string will be added at the end of example.txt file (but not in the separate line).

Alternative solution

In this example, we use fs.writeFileSync() as an alternative solution to fs.writeFile(). The API also replaces the contents of the file if it does already exist.

const fs = require('fs');

const number = 123;
const data = number.toString();

try {
  const result = fs.writeFileSync('./example.txt', data); // fs.writeFileSync(path, string);
} catch (error) {
  console.error(error);
}

References

• File system | Node.js v16.8.0 Documentation