brainLuck - www.codewars.com/dojo/katas/526156943dfe7ce06200063e/play/javascript

brainLuck.js

function brainLuck(code, input){
  var dp = 0, output = [], value = 0, data='', ip=0, braceCount = 0;
  for(var i=0, l= code.length; i < l; i++) {
    switch(code[i]){
      case '>':
        dp++;
        if(dp >= data.length) {
          data += String.fromCharCode(0);
        }
        break;
      case '<':
        dp--;
        if(dp < 0) {
          data = String.fromCharCode(0) + data;
          dp = 0;
        }
        break;
      case '+':
        value = (data.charCodeAt(dp)||0) + 1;
        if(value>255) value = 0;
        data = data.substr(0,dp) + String.fromCharCode(value) + data.substr(dp+1);
        break;
      case '-':
        value = (data.charCodeAt(dp)||0) - 1;
        if(value<0) value = 255;
        data = data.substr(0,dp) + String.fromCharCode(value) + data.substr(dp+1);
        break;
      case '.':
        output.push(data[dp]);
        break;
      case ',':
        data = data.substr(0,dp) + String.fromCharCode(input.charCodeAt(ip++)||0) + data.substr(dp+1);
        break;
      case '[':
        value = data.charCodeAt(dp);
        if(!value){
          braceCount = 1;
          i++;
          while(i<l && braceCount>0) {
            if(code[i]==='[') braceCount++;
            if(code[i]===']') braceCount--;
            i++;
          }
        }
        break;
      case ']':
        value = data.charCodeAt(dp);
        if(value){
          braceCount = 1;
          i--;
          while(i>=0 && braceCount>0) {
            if(code[i]==='[') braceCount--;
            if(code[i]===']') braceCount++;
            i--;
          }
        }
        break;
    }
  }
  return output.join('');
}