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Node.js by Example

Buffers

Buffers are a series of bytes.

What does that mean?

If you are completely new to computer programming/science, here's a quick intro to Bits, Bytes and Octets.

Buffers

Pure JavaScript is Unicode friendly but not nice to binary data. When dealing with TCP streams or the file system, it's necessary to handle octet streams. Node has several ways of manipulating, creating, and consuming octet streams.

Buffers are used internally by Node.js but available to everyone.

Here's a simple example of creating a new Buffer containing the word "hello". You will notice that the buffer stores the the hexadecimal values for the characters.

new Buffer(size)

Allocates a new buffer of size octets.

Feeding new Buffer() a numeric parameter simply allocates that amount of memory to the buffer for later use.

var buf = new Buffer(10); // <Buffer 10 d6 33 00 01 00 00 00 00 c8>
var str = buf.toString(); // �3�  (incomprehensible - non-printable chars)

Practical use? None. (If I find one I will let you know.)

new Buffer(array)

Allocates a new buffer using an array of octets.

Similar to the new Buffer(number) but allows you to pass in an array; node creates a placeholder for each element in the array in your new Buffer.

var buf = new Buffer(['hello','world']); // <Buffer 00 00>
var str = buf.toString(); // empty

Practical use? None.

new Buffer(str, [encoding])

  • str String - string to encode.
  • encoding String - encoding to use, Optional.

Allocates a new buffer containing the given str. encoding defaults to 'utf8'.

var buf = new Buffer('hello'); // <Buffer 68 65 6c 6c 6f>
var str = buf.toString();      // hello

Class Method: Buffer.isEncoding(encoding)

  • encoding String The encoding string to test

Returns true if the encoding is a valid encoding argument, or false otherwise.

console.log("Buffer.isEncoding('utf8') >> " + Buffer.isEncoding('utf8') ); // true

Again, can't see a practical application for this.

buf.toJSON()

Returns a JSON-representation of the Buffer instance, which is identical to the output for JSON Arrays. JSON.stringify implicitly calls this function when stringifying a Buffer instance.

var buf = new Buffer('test');
var json = JSON.stringify(buf);

console.log(json); // '[116,101,115,116]'

var copy = new Buffer(JSON.parse(json));

console.log(copy); // <Buffer 74 65 73 74>