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What is Buffer in Node.js?

What is Buffer in Node.js?

In this comprehensive guide, we will delve deep into the world of Buffers in Node.js, exploring their significance, functionalities, and practical applications.

Table of Contents

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What is Binary Code?

Binary code is a fundamental concept in computer science and information technology. It represents data and instructions using only two digits: 0 and 1. These digits are known as binary digits or bits.

In contrast to the decimal system, which uses base 10 with digits ranging from 0 to 9, the binary system operates on base 2, where each digit’s value is a power of 2. For example, the rightmost bit represents 2^0 (1), the next bit represents 2^1 (2), followed by 2^2 (4), 2^3 (8), and so on.

Computers use binary code internally because electronic devices can easily represent two states, such as high voltage (1) and low voltage (0). Binary code allows computers to store and process information by manipulating these binary digits. All data types, such as numbers, characters, images, and program instructions, are ultimately represented in binary form.

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What is Node.js Buffer?

What is Node.js Buffer

Node.js empowers developers to execute JavaScript code on the server-side, serving as a robust JavaScript runtime environment. An essential element introduced by Node.js is the Buffer, a special object facilitating efficient manipulation of binary data. Buffers are instances derived from the Buffer class, an integral component of the Node.js core modules.

A buffer is a fixed-sized portion of memory designated to store unprocessed binary data. Its purpose revolves around providing a temporary storage space that enables both reading and writing operations. Buffers prove particularly advantageous when engaged in network operations, file systems, and other scenarios demanding the direct handling of binary data.

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The Buffer Class in Node.js

The Buffer class in Node.js encapsulates the functionality for manipulating binary data. It provides a range of methods and properties that enable developers to create, read, and modify data stored in buffers.

In order to establish a buffer, one can employ diverse techniques like utilizing the `Buffer.from()`, `Buffer.alloc()`, or `Buffer.allocUnsafe()` methods. The `Buffer.from()` method enables the creation of a buffer from a pre-existing data source, such as a string or an array of numbers. On the other hand, the `Buffer.alloc()` method generates a fresh buffer with a designated size, whereas the `Buffer.allocUnsafe()` method allocates a new buffer without initializing its contents. This may result in enhanced performance, albeit requiring a manual data population.

Once you have a buffer, you can use methods like `buffer.toString()` to convert it back to a string, `buffer.readUInt8()` to read an 8-bit unsigned integer from the buffer, or `buffer.writeUInt16BE()` to write a 16-bit unsigned integer to the buffer. These methods and many others provided by the Buffer class allow developers to manipulate binary data efficiently.

In addition to its various encoding options like UTF-8, ASCII, and Base64 for seamless conversion between different character representations and binary data, the Buffer class provides methods for comparing buffers, concatenating buffers, filling buffers with a specified value, and more.

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Node.js buffer methods

Node.js buffer methods

One noteworthy aspect of the Node.js buffer module is its independence from importation into the application prior to utilizing its methods. Allow us to examine a few significant Node.js buffer methods that necessitate familiarity.


In Node.js, developers employ the Buffer.alloc() method to generate a new Buffer object of a designated size. This method accepts the desired size as an argument and yields a new Buffer instance with the allocated memory.

Utilizing this method proves advantageous when there is a need to reserve memory for a buffer without initializing its contents. The allocated memory is automatically populated with zeros as the default behavior.

For example, suppose you must create a buffer of size 10 bytes. You can use the Buffer.alloc() method as follows:

const buffer = Buffer.alloc(10);

The code allocates 10 bytes of memory to create a new Buffer object. It initializes the buffer with zeros, enabling you to store data in it subsequently.


The Buffer.write() method writes a string or buffer data into a buffer object. Its first parameter denotes the data to be written, while the second and third parameters, which are optional in nature, represent the offset and length correspondingly. The offset parameter designates the buffer index where the data shall be written, whereas the length parameter determines the byte count to be written.

Here’s an example that demonstrates the usage of Buffer.write():

const buffer = Buffer.alloc(10);
const data = 'Hello, World!';
buffer.write(data, 0, data.length);

In this code, we create a new buffer of size 10 using Buffer.alloc(). Then, we write the string ‘Hello, World!’ into the buffer starting from the beginning (offset 0) and considering the length of the data string. The Buffer.write() method automatically handles any necessary conversions to properly encode the data into the buffer.

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The Buffer.byteLength() method is used to determine the number of bytes occupied by a string in a buffer. It takes a string as its parameter and returns the number of bytes required to store that string in the buffer.

Consider the following example:

const string = 'Hello, World!';
const length = Buffer.byteLength(string);

In this code, we intend to store the string ‘Hello, World!’ in a buffer. By utilizing the Buffer.byteLength() method, we can acquire the precise count of bytes needed to accommodate the string within the buffer. The variable ‘length’ will hold a value equivalent to the number of bytes required for storing the string.


The Buffer.compare() method in Node.js allows you to compare two buffers and determine their relative order. This method comes in handy when you need to sort or compare buffers based on their contents. The Buffer.compare() function takes two buffer objects as arguments and returns an integer indicating the result of the comparison.

When comparing two buffers, Buffer.compare() follows the same rules as the standard JavaScript comparison algorithm. It performs a byte-by-byte comparison starting from the first byte of each buffer. The comparison stops as soon as a difference is encountered between the bytes being compared. If the two buffers are equal, the method returns 0. If the first buffer comes before the second buffer in the sorting order, a negative value is returned. Conversely, if the second buffer comes before the first one, a positive value is returned.

Here’s an example to illustrate the usage of Buffer.compare():

const buffer1 = Buffer.from('Hello');
const buffer2 = Buffer.from('World');
const result = Buffer.compare(buffer1, buffer2);
if (result < 0) {
  console.log('buffer1 comes before buffer2');
} else if (result > 0) {
  console.log('buffer2 comes before buffer1');
} else {
  console.log('buffer1 and buffer2 are equal');

In this example, we create two buffers, `buffer1` and `buffer2`, containing the strings ‘Hello’ and ‘World’, respectively. We then use `Buffer.compare()` to compare the two buffers. The result is stored in the `result` variable. Depending on the comparison result, we print the appropriate message to the console.


The method Buffer.concat() enables the concatenation of multiple buffers into a single buffer. It proves especially advantageous in scenarios where an array of buffers needs to be merged into a larger buffer. By providing an array of buffer objects as its argument, the method yields a new buffer that encompasses the combined data.

Here’s an example to demonstrate the usage of Buffer.concat():

const buffer1 = Buffer.from('Hello');
const buffer2 = Buffer.from('World');
const buffer3 = Buffer.from('!');
const combinedBuffer = Buffer.concat([buffer1, buffer2, buffer3]);

In this example, we create three buffers: `buffer1`, `buffer2`, and `buffer3`, representing the strings ‘Hello’, ‘World’, and ‘!’, respectively. We then use `Buffer.concat()` to combine these three buffers into a single buffer called `combinedBuffer`. Finally, we convert the `combinedBuffer` back to a string using the `toString()` method and print the result to the console.


The buf.entries() method yields an iterator enabling you to actively iterate through the buffer’s contents. It offers a convenient means to access the index-value pair of each byte within the buffer.

Here’s an example to demonstrate the usage of buf.entries():

const buffer = Buffer.from('Hello');
for (const [index, value] of buffer.entries()) {
  console.log(`Index: ${index}, Value: ${value}`);

In this example, a buffer named `buffer` is created, which holds the string ‘Hello’. Subsequently, we utilize the `entries()` method to acquire an iterator. Through the utilization of a for loop, we actively iterate over each entry within the buffer. The `index` variable denotes the byte’s index, while the `value` variable signifies the byte’s value at said index. The console is used to display the index and value of each entry.

The `buf.entries()` method streamlines the iteration process over the contents of a buffer and empowers you to execute diverse operations on the individual bytes. It proves exceptionally valuable when a methodical approach is required to process or analyze the buffer’s contents.


The Buffer.fill() method is a powerful tool provided by the Buffer class in Node.js. Its purpose is to fill a specified range of a buffer with a given value. This method is particularly useful when you need to initialize a buffer with a specific pattern or when you want to overwrite existing data within a buffer.

When using Buffer.fill(), you pass in three parameters: the value you want to fill the buffer with, the starting index from where the filling should begin, and the ending index where the filling should stop. The value can be a number ranging from 0 to 255, representing the ASCII value of the character, or it can be a string.

For example, let’s say we have a buffer named `buf` of length 10. To fill the entire buffer with the value 0, we can use the following code:

const buf = Buffer.alloc(10);

In this scenario, invoking the function `buf.fill(0)` actively assigns a value of 0 to every individual byte within the buffer. Should there be a requirement to solely fill a designated segment of the buffer, it is possible to specify the starting and ending indices. For example, to fill the initial 5 bytes of the buffer with the value 1, the following procedure can be employed:

buf.fill(1, 0, 5);

This will modify only the bytes at indices 0 to 4, leaving the rest of the buffer untouched.


The Node.js feature of Buffer.from() enables the creation of a new buffer object from a pre-existing data source. This method demonstrates exceptional versatility by accommodating multiple data types, such as strings, arrays, and buffers. It presents a convenient means of converting data into a buffer format, allowing for subsequent manipulation and processing through the utilization of other Buffer methods.

In order to utilize Buffer.from(), you provide the data source as the first parameter and an optional encoding as the second parameter. The encoding parameter designates the character encoding of the data source, such as ‘utf8’ or ‘base64’. If no encoding is explicitly specified, the default ‘utf8’ encoding will be applied.

Here’s an example that demonstrates creating a buffer from a string:

const str = 'Hello, World!'; 
const buf = Buffer.from(str, 'utf8');

In this scenario, the encoding ‘utf8’ is utilized to convert the string ‘Hello, World!’ into a buffer. Consequently, one can now manipulate and access the resulting buffer, named `buf`, by employing the diverse methods offered by the Buffer. The usage of Buffer.from() proves beneficial when the necessity arises to duplicate the contents of an existing buffer into a fresh buffer. By utilizing an existing buffer as the data source, one can generate an exact replica of the initial buffer.

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The buf.includes() method is used to check whether a specific value or pattern exists within a buffer. It returns a boolean value indicating whether the value is found or not. This method is helpful when you need to perform searches or validations on the data stored in a buffer.

To use buf.includes(), you provide the value you want to search for as the first parameter and an optional starting index as the second parameter. The starting index determines the position within the buffer to begin the search. If no starting index is specified, the search starts from the beginning of the buffer.

Here’s an example to illustrate the usage of buf.includes():

const buf = Buffer.from('Hello, World!', 'utf8');
console.log(buf.includes('World'));  // Output: true
console.log(buf.includes('OpenAI')); // Output: false

In this case, we create a buffer from the string ‘Hello, World!’ and perform two searches using buf.includes(). The first search checks if the string ‘World’ is present in the buffer, returning true. The second search looks for the string ‘OpenAI’, which is not found in the buffer, resulting in a false value.

It’s important to note that buf.includes() performs a byte-level search within the buffer. If you’re working with multibyte characters or encodings like UTF-8, you need to consider the byte representation of the value you’re searching for.

By utilizing buf.includes(), you can efficiently search for values within a buffer, enabling you to perform various operations and logic based on the presence or absence of specific data.


The Buffer.isEncoding() method in Node.js is a useful utility that allows developers to determine whether a given encoding is supported by the Buffer class. When working with binary data, it’s crucial to ensure that the encoding used is compatible to avoid any potential data corruption or loss.

To use Buffer.isEncoding(), you pass an encoding string as an argument to the method. It will then return a boolean value indicating whether the specified encoding is supported or not. This method is particularly helpful when you need to validate and handle user input or when dealing with external data sources that might use different encodings.

For example, let’s say you want to check if the encoding “utf-8” is supported. You would use the following code:

const encoding = 'utf-8';
const isSupported = Buffer.isEncoding(encoding);
if (isSupported) {
  console.log(`The encoding ${encoding} is supported.`);
} else {
  console.log(`The encoding ${encoding} is not supported.`);

By utilizing Buffer.isEncoding(), you can ensure that the encoding used in your application is valid and supported, enhancing the reliability and compatibility of your codebase.


The buf.slice() method in Node.js provides a way to extract a portion, or slice, of a buffer without making a full copy of the original data. This method is beneficial when you only need a subset of the buffer’s contents, saving memory and improving performance.

To use buf.slice(), you need to specify the starting and ending indexes of the portion you want to extract. The method returns a new buffer containing the extracted data, allowing you to manipulate or work with the subset independently.

Here’s an example that demonstrates the usage of buf.slice():

const buffer = Buffer.from('Hello, World!');
const slicedBuffer = buffer.slice(0, 5);
console.log(slicedBuffer.toString()); // Output: Hello

In the above code, we create a buffer with the string ‘Hello, World!’. We then use buf.slice(0, 5) to extract the first five bytes of the buffer, which represents the substring ‘Hello’. Finally, we convert the sliced buffer back to a string using the toString() method and log the result.

By utilizing buf.slice(), you can efficiently extract and manipulate specific portions of a buffer, optimizing memory usage and improving the overall performance of your application.

Buffer Swap

Buffer Swap is a concept that refers to the exchange of data between two buffers. It allows you to transfer the content of one buffer to another without copying the data explicitly. This can be particularly useful in scenarios where you need to rearrange or manipulate data in different parts of your application.

To perform a buffer swap, you need two buffer objects. You can use various methods to achieve the swap, such as the buffer.copy() method or direct assignment using the assignment operator (=). The key idea is to ensure that the content of one buffer is moved to the other buffer and vice versa, effectively swapping their data.

Here’s an example that demonstrates a buffer swap using the buffer.copy() method:

const buffer1 = Buffer.from('Hello');
const buffer2 = Buffer.from('World');
console.log(buffer1.toString()); // Output: World
console.log(buffer2.toString()); // Output: Hello

In the code above, we create two buffers- buffer1 and buffer2, with the contents ‘Hello’ and ‘World’, respectively. We then use buffer1.copy(buffer2) to swap the content between the two buffers. After the swap, buffer1 contains ‘World’ and buffer2 contains ‘Hello’.

By leveraging buffer swap techniques, you can efficiently manipulate and rearrange data between buffers, facilitating various operations within your Node.js applications.


The buf.json() method is a convenient feature in Node.js that allows you to convert a buffer to its JSON representation. JSON (JavaScript Object Notation) is a widely-used data interchange format that provides a lightweight and human-readable way to represent structured data.

To use buf.json(), you simply call the method on a buffer object. It returns a JSON representation of the buffer’s data, which can be further processed or transmitted as needed. This method is especially useful when you need to convert binary data to a format that can be easily consumed by other systems or when interacting with APIs that expect JSON data.

Here’s an example illustrating the usage of buf.json():

const buffer = Buffer.from('{"name":"John","age":30}');
const jsonData = buffer.json();
console.log(jsonData); // Output: { name: 'John', age: 30 }

By employing the buf.json() method, one can effortlessly convert buffer data into a JSON format, thereby facilitating smooth integration with other systems and enabling efficient data exchange.

Buffer Offset Read

Buffer Offset Read refers to the process of extracting data from a buffer at a specific offset or position. In other words, it allows you to read data from a specific location within a buffer rather than starting from the beginning. This functionality is particularly useful when dealing with large buffers or when you need to access specific data within a buffer without iterating through the entire buffer.

To perform a buffer offset read, you need to specify the offset position from where you want to read the data and the length of the data you want to extract. The offset is typically specified in bytes and represents the starting point for reading the data. The length parameter determines the number of bytes to be read from the buffer.

The buffer offset read operation comprises two primary steps. Initially, one must generate a buffer object that encompasses the desired data by employing either the `Buffer.from()` method or by allocating a new buffer through the `Buffer.alloc()` method. Subsequently, utilizing the `buffer.slice()` method, a new buffer can be created, representing a section of the original buffer, commencing from the designated offset.

For example, consider the following code snippet:

const buffer = Buffer.from('Hello, World!');
const offset = 7;
const length = 5;
const data = buffer.slice(offset, offset + length);
console.log(data.toString()); // Output: World

In this example, we create a buffer from the string ‘Hello, World!’ and specify an offset of 7 and a length of 5. The `buffer.slice()` method is used to extract the portion of the buffer starting from the offset position and spanning the specified length. Finally, we convert the extracted data to a string and print it, which outputs ‘World’.

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Buffer Offset Write

Buffer offset writes allow you to write data to a specific offset or position within a buffer. This enables you to update or insert data at a specific location, rather than overwriting the entire buffer or appending data at the end. It provides flexibility and efficiency when working with buffers, especially when dealing with large data sets or when precise data manipulation is required.

In order to execute a buffer offset write, you must indicate the desired position for writing the data and provide the data itself. Typically, you would specify the offset in bytes, which denotes the initial location for writing the data. The data may encompass a string, a buffer, or any other suitable data type that can be converted into a buffer.

The buffer offset write operation comprises two essential steps. Firstly, one must create a buffer object to store the data. This can be achieved by employing the `Buffer.alloc()` method to allocate a new buffer or by utilizing the `Buffer.from()` method to generate a buffer from preexisting data. Once the buffer is obtained, the data can be copied into the original buffer at the designated offset using the `buffer.copy()` method.

const buffer = Buffer.alloc(15);
const data = 'Hello, World!';
const offset = 7;
buffer.write(data, offset);
console.log(buffer.toString()); // Output: [empty][empty][empty]Hello, World!

In this example, we utilize the `Buffer.alloc()` function to actively create an empty buffer measuring 15 bytes in length. Subsequently, we designate the string ‘Hello, World!’ as the data to be written, while also specifying an offset of 7. Employing the `buffer.write()` method, we actively inscribe the data into the buffer at the indicated offset. Ultimately, we transform the buffer into a string and formally display it, resulting in the output ‘[empty][empty][empty]Hello, World!’, with each ‘[empty]’ symbolizing unoccupied bytes within the buffer.

Buffer offset write allows you to selectively update or insert data at specific positions within a buffer, providing fine-grained control over the buffer contents. This capability is particularly useful when dealing with binary data or when performing low-level manipulations in applications such as file systems, network protocols, or data serialization.


Buffers in Node.js provide an essential mechanism for dealing with binary data, enabling developers to work with non-textual information efficiently and seamlessly integrate Node.js applications into various data-centric environments. Understanding and utilizing buffers effectively can significantly enhance the performance and reliability of Node.js applications in a wide range of scenarios.

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