how base64 encoding and decoding is done in nodejs

Base64 is a binary-to-text encoding scheme that represents binary data in an ASCII string format. It's commonly used when you need to transmit binary data over media that are designed to handle textual data, such as email or HTTP headers. Essentially, it provides a way to ensure that binary data is treated as a string and avoids potential corruption or interpretation issues during transmission.

**1. Understanding Base64 Principles**

* **The Base64 Alphabet:** Base64 uses a set of 64 characters:
* A-Z (26 characters)
* a-z (26 characters)
* 0-9 (10 characters)
* + (plus sign)
* / (forward slash)

* **Padding:** The "=" (equals sign) is used as padding if the input data is not a multiple of 3 bytes. Padding ensures that the encoded output is always a multiple of 4 characters.

* **Encoding Process:**
1. The input data is divided into groups of 3 bytes.
2. Each group of 3 bytes (24 bits) is treated as four 6-bit values.
3. Each 6-bit value is then mapped to a character in the Base64 alphabet using its index (0-63).
4. If the input data's length is not a multiple of 3, padding characters (=) are added to the end of the encoded output to make its length a multiple of 4.

* **Decoding Process:** The reverse of the encoding process. The Base64 string is split into groups of four characters. Each character is converted back to its corresponding 6-bit value. These 6-bit values are concatenated and then split into 8-bit bytes, reconstructing the original binary data. Padding characters are removed during decoding.

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