Brainfuck interpreter in JavaScript

gistfile1.js

var fs = require('fs');

var Brainfuck = function () {
};

Brainfuck.prototype.init = function() {
  this.data = new Array(30000);

  for(var i = 0; i < this.data.length; i++) {
    this.data[i] = 0;
  }

  this.dataPointer = 0;
  this.instructionPointer = 0;
};

Brainfuck.prototype.run = function(code) {
  this.init();

  while (this.instructionPointer < code.length) {
    switch(code[this.instructionPointer]) {
      case '>':
        this.dataPointer++;
        break;
      case '<':
        this.dataPointer--;
        break;
      case '+':
        this.data[this.dataPointer]++;
        break;
      case '-':
        this.data[this.dataPointer]--;
        break;
      case '.':
        process.stdout.write(String.fromCharCode(this.data[this.dataPointer]));
        break;
      case ',':
        var response = fs.readSync(process.stdin.fd, 100, 0, "utf8");
        this.data[this.dataPointer] = response[0].charCodeAt(0);
        break;
      case '[':
        if (this.data[this.dataPointer] === 0) {
          this.instructionPointer = this.findMatching(code, ']', '[', 1);
        }
        break;
      case ']':
        if(this.data[this.dataPointer] !== 0) {
          this.instructionPointer = this.findMatching(code, '[', ']', -1);
        }
        break;
      default:
        throw new Error("Unknown opcode " + code[this.instructionPointer]);
    }

    this.instructionPointer++;
  }
};

Brainfuck.prototype.findMatching = function(code, a, b, increment) {
  var skip = 0;

  for(var i = this.instructionPointer + increment; i < code.length; i += increment) {
    if (code[i] === b) {
      skip++;
    } else if (code[i] === a && skip === 0) {
      return i;
    } else if(code[i] === a) {
      skip--;
    }
  }

  return i;
};

var br = new Brainfuck();

// Hello World
br.run('++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.');

// Merry freakin' Christmas
br.run('>+++++++[<+++++++++++>-]<.>++++[<++++++>-]<.>+++[<++++>-]<+..+++++++.>++++++++[<----------->-]<-.>+++++++[<++++++++++>-]<.>++[<++++++>-]<.>++[<------>-]<-.----.>+++++[<++>-]<.--.+++++.>+++++++[<---------->-]<-.-------.>+++++++[<+++++>-]<.>++++++++[<++++>-]<+++++.>++[<+++++>-]<.>+++[<--->-]<.>++[<+++++>-]<.+.>++[<---->-]<+.>+++[<---->-]<.>+++[<++++++>-]<.');

// ROT13
br.run('-,+[-[>>++++[>++++++++<-]<+<-[>+>+>-[>>>]<[[>+<-]>>+>]<<<<<-]]>>>[-]+>--[-[<->+++[-]]]<[++++++++++++<[>-[>+>>]>[+[<+>-]>+>>]<<<<<-]>>[<+>-]>[-[-<<[-]>>]<<[<<->>-]>>]<<[<<+>>-]]<[-]<.[-]<-,+]');