Rename a file if already exists in javascript by increment file_1.txt,file_2.txt like that. This code didn't works

Question

I tried this code, It creates a file like file.txt as file_1.txt after that it didn't increased it ,again i gave a filename as file.txt it again shows file_1.txt. I need to increase the value like file_1.txt,file_2.txt,file_3.txt like that.

 while (await client.exists(path+'/'+filename)) {
        var ext = filename.split('.');
        if (i == 0) {
            i = i + 1;
            filename = ext[0] + "_" + i + "." + ext[1]
            i++;
            var newfilename = filename
            // await client.put(buff,path+'/'+newfilename)
            console.log(newfilename)
           
        } else {
            file = ext[0].substr(0, ext[0].lastIndexOf("_" + i));
            i = i + 1;
            filename = filename + "_" + i + "." + ext[1]
        }

    }

Answer 1

I can't see from the code where you get your index or i from

var newIndex
var newFilename

function addNewFilename(fileName) {
  // find index with regex match number
  let number = fileName.match(/\d+/)

  // if number exist just increase the index
  if (number != null) {
    let currentIndex = number[0]
    newIndex = +currentIndex + 1
    return newFilename = fileName.replace(/\d+/, newIndex);
  }
  // if number is null we add '_1'
  else {
    newIndex = '_1'
    let ext = fileName.split('.')
    return newFilename = ext[0] + newIndex + '.' + ext[1]
  }
}

let file1 = addNewFilename('file.txt')
let file2 = addNewFilename('file_1.txt')
let file3 = addNewFilename('file_31.txt')

console.log('file1:', file1)
console.log('file2:', file2)
console.log('file3:', file3)

Answer 2

You can try this

function getNewFileName(fileName){
  const [name, ext] = fileName.split('.');
  const nameParts = name.split('_');
  let suffixNumber = '';
  if(nameParts.length > 1){
    //name has _n suffix 
    const n = Number(nameParts.pop());
    suffixNumber = n+1;
  
    fileName = nameParts.pop()+'_'+suffixNumber;
  }
  else{
    //name does not have number suffix, so assign it to 1, so that fileName would be file_1.ext
    suffixNumber = 1;
    fileName = nameParts.pop()+'_'+suffixNumber;
  }
  console.log(fileName);
}

// Just to show the output in the console
//  Remove these lines once adding this code to your file
getNewFileName('file.jpg');
getNewFileName('file_1.jpg');
getNewFileName('file_2.jpg');
getNewFileName('file_3.jpg');
//----------

And you can use this as below

while (await client.exists(path+'/'+filename)) {
    filename = getNewFileName(filename);
}