How to read files with Node.js?

In this tutorial, we will explore different ways we can read files in Node.js.  

In software development, reading files is a regular part of the job. However, this simple process very often becomes complicated and tedious. Fortunately, that’s not the case in Node.js. Node.js provides a built-infile system(fs) module, to carry out file operations. 

Before we start, let us make sure we have the basic prerequisites. You will need to ensure you have: 

For this tutorial, my environment setup includes: 

fs module is a built-in module in the Node.js. You do notnecessarily need to install it.  

The fs module supports both Synchronous and Asynchronous function calls. 

I am assuming you have installed the NodeJS. 

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Open this directory in the code editor. 

From the index.js, we will read the test.txt.  

The readFileSync is a synchronous method to read a file. 

Syntax 

fs.readFileSync(path[, options]) 

Open index.js in the Code Editor. 

Paste the below code.

Open the terminal or cmd in the node-fs directory and run the below command.

It has returned the content in the buffer format. The readFileSync by default returns the content in the Buffer format.

To get the content in normal string format, we need to pass the utf8 encoding as a parameter.

Change the code.

run it.

Read file Asynchronously using readFile

Asynchronous methods are great when you don’t want to wait for a process to complete.  
fs module provides an asynchronous method to read a file. It returns a callback.
Syntax

Syntax is similar tothe synchronous method except it returns a callback function.

Run the code.

Reading file using fs.readFileis an ideal way if the file size is less. If the size is huge, the read will consume the complete Memory and you may find your system hanging. 

In such scenarios, Stream is the best option. This breaks the file into small chunks of data and sends a piece at a time. In this way, the system can continue with other tasks without allocating the complete memory to it.   

Let us code and understand. 

Node.js provides a createReadStreammethod to stream the file. createReadStreamreturns a fs.ReadStreamobject. The readStream events like data, end, or error. To read the file, we have to listen to these events.  

Run the code.

For the purpose of the experiment, I created a file of 20MB to check the performance of readFileSync, readFileand createReadStream.  

The average memory consumption of VS Code is 600-700MB in my machine. 

This is a screenshot before running any of the commands. 

Check the screenshot. This operation took 373MB and it went on to upto ~450MB. 

Check the screenshot. This operation took 506MB and it went on to upto ~600MB.

Check the screenshot. This operation took 287MB and it reached upto ~300MB.  

Node.js provides multiple methods to read a file. It completely depends on the file size and the requirement, which method to choose. From our performance tests, streaming turns out to be the most efficient method to use.  

The performance may vary from machine to machine and file size. One must note that what we have demonstrated is just for the sake of a demo, so this must not be taken to be the final words. There are other npm packages available for file system, for example,fs-extra.  

Hope this tutorial has helped. Taking a formal training course in Node.js would be a great way to fast-track your career.  

Happy coding!

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