Checking file existence and stats in Node.js - Step-by-Step Execution

Concept Flow - Checking file existence and stats

Start

↓

Call fs.stat(path)

↓

Does file exist?

Yes No↓

Get stats

↓

Use stats

↓

End

This flow shows how Node.js checks if a file exists by calling fs.stat, then either gets file stats or handles the error if the file is missing.

Execution Sample

Node.js

import { stat } from 'node:fs/promises';

async function checkFile(path) {
  try {
    const stats = await stat(path);
    return stats.isFile();
  } catch {
    return false;
  }
}

This async function checks if a file exists at the given path and returns true if it is a file, false otherwise.

Execution Table

Step	Action	Evaluation	Result
1	Call stat(path)	Does file exist at path?	Yes or No
2	If Yes	Retrieve stats object	stats object with file info
3	Call stats.isFile()	Is it a file?	true or false
4	If No (error thrown)	Catch error	Return false
5	Return result	true if file, false if not	Function returns boolean

💡 Function ends after returning true or false based on file existence and type

Variable Tracker

Variable	Start	After stat call	After catch	Final
path	'some/path.txt'	'some/path.txt'	'some/path.txt'	'some/path.txt'
stats	undefined	stats object	undefined	stats object or undefined
result	undefined	undefined	false	true or false

Key Moments - 3 Insights

Why do we use try/catch around stat()?

Because stat() throws an error if the file does not exist, so try/catch lets us handle that case gracefully (see execution_table step 4).

What does stats.isFile() check?

It checks if the path points to a regular file, not a directory or other type (see execution_table step 3).

Why return false in the catch block?

Because an error means the file doesn't exist or can't be accessed, so returning false signals no valid file (see execution_table step 4).

Visual Quiz - 3 Questions

Look at the execution table, what happens at step 3?

A Retrieve stats object

B Check if stats is a file

C Catch error if file missing

D Return false

💡 Hint

Refer to execution_table row with Step 3 describing stats.isFile() check

At which step does the function handle the file not existing?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look at execution_table row 4 where catch handles errors

If the file exists but is a directory, what will the function return?

A false

B true

C throws error

D undefined

💡 Hint

Check variable 'result' after stats.isFile() returns false for directories

Concept Snapshot

Use fs.stat(path) inside try/catch to check file existence.
If stat succeeds, use stats.isFile() to confirm it's a file.
If stat throws error, file doesn't exist; return false.
This async pattern safely checks file presence and type.

Full Transcript

This lesson shows how to check if a file exists and get its stats in Node.js using the fs/promises module. The key function is stat(path), which returns file info if the file exists or throws an error if it doesn't. We use try/catch to handle this error. If stat succeeds, we call stats.isFile() to check if the path is a file. The function returns true if it is a file, otherwise false. This approach avoids crashes and clearly signals file presence.