Replace word from multiple .txt files in nodejs

Question

In a directory there are multiple files with different extensions. I have to find and select .txt files and from these all .txt files there are some words I have to replace with new words.

say , 4 files from my directory are :

File1.txt
File2.txt
File3.txt
File4.txt

now I have to replace word 'mobile' to 'laptop' from all .txt files

than again I have to replace word 'School' to 'College' from all txt.files

and again replace word 'banana' to 'Mango' from all txt.files

and then save the file.

const path = require('path')
const fs = require('fs')

const dirpath = path.join(__dirname, '/')

fs.readdir(dirpath, function(err, files) {
  const Files = files.filter(el => path.extname(el) === '.txt')

for (let i=0; i < Files.length; i++) {
      console.log(Files[i])


      var fs = require('fs')
      fs.readFile(Files[i], 'utf8', function (err,data) {
        if (err) {
          return console.log(err);
        }

                var result = data.replace(/mobile/g, 'laptop');
                fs.writeFile(Files[i], result, 'utf8', function (err) {
                  if (err) return console.log(err);
                });

                var result2 = data.replace(/School/g, 'College');
                fs.writeFile(Files[i], result2, 'utf8', function (err) {
                  if (err) return console.log(err);
              });
     
      });

    }

When I run this program only 2nd replace part is working,what should I do!

`replace` returns a new string and doesn't modify the original string. And you are both times calling `replace` on the original `data`. You should call `result2 = result.replace(...)` Furthermore I'd suggest to ditch that first `writeFile` because 1) it's async and will mess up things if you don't wait for it properly and 2) it's unnecessary because you are writing to the same file twice — derpirscher, Jun 19 '22 at 17:50

score 1 · Accepted Answer · answered Jun 19 '22 at 18:07

By doing

var result = data.replace(/mobile/g, 'laptop');
fs.writeFile(Files[i], result, 'utf8', function (err) {
    if (err) return console.log(err);
});

var result2 = data.replace(/School/g, 'College');
fs.writeFile(Files[i], result2, 'utf8', function (err) {
    if (err) return console.log(err);
});

you're

first, saving the first replaced text to the file
then, replacing the original text with the second string, and saving that to the file

Not sure what you were trying to achieve with that first write - if you really wanted two writeFiles, you'd need to wait for the first to finish, and then call readFile again to get the new content, and then call .replace on that content. But why not just ditch that first writeFile entirely and use the string you already have a reference to? (Don't replace data, the original string, but result, the result of the first replacement - or, don't create an intermediate variable at all)

fs.readFile(Files[i], 'utf8', function (err, data) {
    if (err) {
        return console.log(err);
    }
    const result = data
        .replace(/mobile/g, 'laptop')
        .replace(/School/g, 'College');
    fs.writeFile(Files[i], result, 'utf8', function (err) {
        if (err) return console.log(err);
    });
});

If you wanted to have an indicator when all files have been replaced, use the fs.promises API and Promise.all instead of the callback-based API.

Replace word from multiple .txt files in nodejs

1 Answers1