Getting errors trying to create a new file using different methods with node fs in an Electron app

Question

I'm trying to create a new file, but both of the methods below throw me an error:

method 1:

fs.writeFile(fullPath, '', (error) => { alert("exist") })

if a file with the specified name exist: console throws exist
if a file with the specified name doesn't exist: console throws exist AND creates the file

method 2:

if (!fs.existsSync(fullPath)) { 
  fs.appendFile(fullPath)
} else {     
  alert("exist")
}

if a file with the specified name exist: console throws exist
if a file with the specified name doesn't exist: it creates the file AND gives me this error DeprecationWarning: Calling an asynchronous function without callback is deprecated.

Question:

What am I doing wrong?

Update:

I also tried this method suggested in the answer below:

// fullPath= 'C:/Users/Name/test.txt'

fs.writeFile(fullPath, '', (error) => {
  if(error) {
    alert("exist")
    return
  }
    alert("created")
})

and I get this:

if a file with the specified name exist: console throws created
if a file with the specified name doesn't exist: console throws created AND creates the file

Update 2:

I managed to make it work in a slightly different way:

if (!fs.existsSync(fullPath)) { 
  fs.writeFileSync(fullPath, '')
} else {
  alert("exist")
}

jens · Accepted Answer · 2018-03-01 00:11:51Z

2

For method 1, you are using fs.writeFile(file, data[, options], callback). So that callback will be called no matter what, alerting 'exists'. You should have a check, something like:

fs.writeFile(fullPath, '', (error) => {
  if(error) {
    alert("exist");
    return;
  }

  // no error, do what you want.
});

Reference: https://nodejs.org/api/fs.html#fs_fs_writefile_file_data_options_callback

For method 2, you are getting the warning because you are calling fs.appendFile without a callback. Either use fs.appendFileSync or give it a callback.

Reference: https://nodejs.org/api/fs.html#fs_fs_appendfile_file_data_options_callback

answered Mar 1, 2018 at 0:11

jens

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3 Comments

Un1 Over a year ago

Thanks for the answer, I updated the question, I still get the error even when it creates the file. I'm a newbie so I'm not sure what I'm doing wrong there. (I don't use semicolons since the project's using webpack)

jens Over a year ago

The callback will be called when it is successful, and when there is an error. The documentation says that fs.writeFile Asynchronously writes data to a file, replacing the file if it already exists. So in case one when it exists it replaces it and then calls callback with error as null. It will alert 'created'. When the file doesn't exist, it does the same thing but only creates the file rather than replacing it. You aren't doing anything wrong other than using alert when you don't need to. You should alert(error) if you really want to know if there is an error.

Un1 Over a year ago

Ahh, got it, thank you for explaining it and helping out. I managed to make it work

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