buffer

The Buffer class provides a way to work with raw binary data directly. Buffers are used when dealing with files, sockets, or binary protocols.

API Surface

Creation

  • Buffer.alloc(size) — allocate a zero‑filled buffer.
  • Buffer.allocUnsafe(size) — allocate without fill (faster, but old data may remain).
  • Buffer.from(array) — from byte array.
  • Buffer.from(string, [encoding]) — from string with encoding (utf8, base64, hex, etc.).

Conversion

  • buf.toString([encoding]) — decode to string.
  • buf.toJSON() — JSON representation.

Indexing

  • buf[i] — get/set byte at index.

Copy & Slice

  • Buffer.concat(list[, totalLength]) — join multiple buffers.
  • buf.slice(start, end) — view into part of the buffer.

Read & Write

  • buf.write(string, [offset], [length], [encoding])
  • buf.readInt8(offset), buf.readUInt16LE(offset), etc.
  • buf.writeInt32BE(value, offset), etc.

Properties

  • buf.length — size in bytes.
  • Buffer.isBuffer(obj) — check type.
  • Buffer.byteLength(string, [encoding]) — size in bytes when encoded.

Examples (English only)

// Create buffers
const b1 = Buffer.alloc(5);
const b2 = Buffer.from("Hello");
const b3 = Buffer.from("SGVsbG8=", "base64");

console.log(b1, b2.toString(), b3.toString());

// Index access
b2[0] = 0x68; // overwrite 'H' with 'h'
console.log(b2.toString());

// Slice & concat
const part = b2.slice(0, 2);
console.log(part.toString());

const joined = Buffer.concat([b2, Buffer.from(" world")]);
console.log(joined.toString());

// Read & write numbers
const buf = Buffer.alloc(4);
buf.writeInt32BE(12345, 0);
console.log(buf.readInt32BE(0));

Notes

  • Prefer Buffer.alloc over allocUnsafe for security and correctness.
  • Buffers are fixed-size; slicing does not copy but creates a view.
  • Always specify encoding (utf8, base64, hex) when converting strings.
  • Use typed read/write methods for structured binary protocols.