node: checking if a file/directory exists

There are a number of ways to check if a file or directory exists in Node, but one of the simplest is the synchronous existsSync method on the fs module. This method returns a boolean value reflecting whether the path exists or not.

It’s worth noting that fs.exists() has been deprecated due to callback incompatibility, however fs.existsSync does not use a callback and therefore is still acceptable.

Example

const fs = require("fs")

if (fs.existsSync("/etc/passwd")) {
  console.log("The path exists.")
} else {
  console.log("The path does not exist.")
}

While this works, interestingly, for checks like this, it’s not the recommended approach:

To check if a file exists without manipulating it afterwards, fs.access() is recommended.

Unlike exists, which determines whether a target is present, access checks for the caller’s access by testing permissions for the file/directory specified by the path argument. If the target will be modified, i.e. the access call precedes a fs.open, fs.write, or fs.read call, this can create a race condition and the recommendation is to simply call those methods directly and handle the error if the file/directory does not exist.¹

The example of checking for a file:

const fs = require("fs")

const path = "/etc/passwd"

fs.access(path, (err) => {
  if (!err) {
    console.log("file exists")
  } else {
    console.log("file does not exist")
  }
})

The example of checking for a file with specific permissions (source):

// Check if the file exists in the current directory, and if it is writable.
fs.access(file, fs.constants.F_OK | fs.constants.W_OK, (err) => {
  if (err) {
    console.error(
      `${file} ${err.code === "ENOENT" ? "does not exist" : "is read-only"}`,
    )
  } else {
    console.log(`${file} exists, and it is writable`)
  }
})

Footnotes

• ¹ For more context as well as some useful examples of what to do (and what not to do), see the Node documentation on fs.access.