Solving File Path Errors in Node.js: Lessons Learned

Working with file paths in Node.js can be tricky and can cause errors if not handled correctly. In this article, I'll discuss the issues I faced while comparing CSV files and how I resolved it.

Background

I was comparing two CSV files using a JavaScript Node.js tool I created, where I used the built-in fs module and a well-known CSV parser library called csv-parser. The plan was to parse the files and compare them programmatically.

const fs = require("fs");
const csv = require("csv-parser");

const currentProducts = [];

fs.createReadStream("../../../../Downloads/current_products.csv")
  .pipe(csv())
  .on("data", (data) => {
    currentProducts.push(data["Product ID"]);
  })
  .on("end", () => {
    console.log(currentProducts);
  });

The Issue

While executing the above code, I encountered the following error:

Error: ENOENT: no such file or directory, open '../../../../Downloads/current_products.csv

Troubleshooting and Simple Fix

After some debugging, I realised that Node.js uses the current working directory for resolving file paths rather than the location of the actual script file. In my case, the script file was located in a different directory than the one I was executing the code from.

To fix this issue, I had two options:

• Ensure that the current working directory (cwd) is the same as where the script is located, and then run the file.
• OR Use absolute paths / environment variables for the file paths.

I chose the second option by using the path module to create an absolute path for me.

const fs = require("fs");
const csv = require("csv-parser");
const path = require("path");

const currentProductsFile = path.resolve(
  `${__dirname}`,
  "../../../../Downloads/current_products.csv"
)

const currentProducts = [];

fs.createReadStream(currentProductsFile)
  .pipe(csv())
  .on("data", (data) => {
    currentProducts.push(data["Product ID"]);
  })
  .on("end", () => {
    console.log(currentProducts);
  });

path.resolve() resolves a sequence of paths or path segments into an absolute path. It's useful when working with file paths, providing a reliable way to get the absolute path of a file or directory regardless of the script's location.

__dirname in Node.js is a global variable that represents the directory name of the current module.

Best Practice

It's always a good practice to know the current working directory of the script, which can be checked by logging process.cwd(). It's also recommended to use absolute paths or environment variables to ensure that the code works reliably across different directories and machines.

The Node.js path module is a great tool to help with building paths, so it's worth checking out.

In summary, when working with file paths in Node.js:

• Remember that Node.js executes from the current working directory.
• Relative paths will resolve based on the current working directory.
• A way to check the current working directory is to log process.cwd()
• Try to use absolute paths or environment variables to avoid issues like this.
• The Node.js path module can help with building absolute paths.

By following these best practices, you can avoid errors and ensure that your code works reliably across different directories and machines.