hangulIME.js

var Hangul = {
  startChar: 'ㄱㄲㄴㄷㄸㄹㅁㅂㅃㅅㅆㅇㅈㅉㅊㅋㅌㅍㅎ'.split(''),
  middleChar: 'ㅏㅐㅑㅒㅓㅔㅕㅖㅗㅘㅙㅚㅛㅜㅝㅞㅟㅠㅡㅢㅣ'.split(''),
  endChar: ' ㄱㄲㄳㄴㄵㄶㄷㄹㄺㄻㄼㄽㄾㄿㅀㅁㅂㅄㅅㅆㅇㅈㅊㅋㅌㅍㅎ'.split(''),
  code: '가'.charCodeAt(0)
}

var HanConv = {
  start: 'rRseEfaqQtTdwWczxvg'.split(''),
  middle: 'k,o,i,O,j,p,u,P,h,hk,ho,hl,y,n,nj,np,nl,b,m,ml,l'.split(','),
  end: ',r,R,rt,s,sw,sg,e,f,fr,fa,fq,ft,fx,fv,fg,a,q,qt,t,T,d,w,c,z,x,v,g'.split(','),
  consonant: 'qwertasdfgzxcv'.split(''),
  vowel: 'yuiophjklbnm'.split('')
}

function isVowel (char) {
  return HanConv.vowel.indexOf(char.toLowerCase()) != -1;
}

function isConsonant (char) {
  return HanConv.consonant.indexOf(char.toLowerCase()) != -1;
}

function getStartIndex (char) {
  var orig = HanConv.start.indexOf(char);
  if(orig != -1) return orig;
  return HanConv.start.indexOf(char.toLowerCase());
}

function getMiddleIndex (char) {
  var orig = HanConv.middle.indexOf(char);
  if(orig != -1) return orig;
  return HanConv.middle.indexOf(char.toLowerCase());
}

function getEndIndex (char) {
  var orig = HanConv.end.indexOf(char);
  if(orig != -1) return orig;
  orig = HanConv.end.indexOf(char.toLowerCase());
  if(orig != -1) return orig;
  return 0;
}

function createHangul (start, middle, end) {
  if (typeof start === 'string' || start instanceof String)
    start = Hangul.startChar.indexOf(start);
  if (typeof middle === 'string' || middle instanceof String)
    middle = Hangul.middleChar.indexOf(middle);
  if (typeof end === 'string' || end instanceof String)
    end = Hangul.endChar.indexOf(end);
  var startCode = start * Hangul.middleChar.length * Hangul.endChar.length;
  var middleCode = middle * Hangul.endChar.length;
  var endCode = end;
  return String.fromCharCode(Hangul.code + startCode + middleCode + endCode);
}

var HangulIME = function () {
  this.startCode = -1;
  this.middleCode = -1;
  this.endCode = 0;
  this.queue = '';
  this.errors = 0;
}

HangulIME.prototype.getChar = function () {
  if (this.middleCode == -1) {
    this.errors ++;
    return Hangul.startChar[this.startCode];
  } else if (this.startCode == -1) {
    this.errors ++;
    return Hangul.middleChar[this.middleCode];
  } else {
    return createHangul(this.startCode, this.middleCode, this.endCode);
  }
}

HangulIME.prototype.pushQueue = function () {
  var char = this.getChar();
  if(char != undefined) this.queue += char;
}

HangulIME.prototype.reset = function () {
  this.startCode = -1;
  this.middleCode = -1;
  this.endCode = 0;
  this.errors = 0;
}

HangulIME.prototype.next = function (char) {
  if(isConsonant(char)) {
    if(this.startCode == -1) {
      // Start code is not set yet
      this.startCode = getStartIndex(char);
    } else if(this.middleCode == -1) {
      // Middle code is not set yet
      // Just reset
      this.pushQueue();
      this.reset();
      this.startCode = getStartIndex(char);
    } else {
      // Set end code
      var endTemp = getEndIndex(HanConv.end[this.endCode] + char);
      if(endTemp == 0) {
        // requested character does not exist
        this.pushQueue();
        this.reset();
        this.startCode = getStartIndex(char);
      } else {
        this.endCode = endTemp;
      }
    }
  } else if(isVowel(char)) {
    if(this.endCode == 0) {
      // Set middle code
      var middleTemp;
      if(this.middleCode == -1) {
        middleTemp = getMiddleIndex(char);
      } else {
        middleTemp = getMiddleIndex(HanConv.middle[this.middleCode] + char);
      }
      if(middleTemp == -1) {
        // Start new char
        this.pushQueue();
        this.reset();
        this.middleCode = getMiddleIndex(char);
      } else {
        this.middleCode = middleTemp;
      }
    } else {
      // Try to 'subtract' end code
      var endChar = HanConv.end[this.endCode];
      var newStart;
      if(endChar.length == 1) {
        this.endCode = 0;
        newStart = getStartIndex(endChar);
      } else {
        this.endCode = getEndIndex(endChar.slice(0, endChar.length-1));
        newStart = getStartIndex(endChar.slice(endChar.length-1));
      }
      this.pushQueue();
      this.reset();
      this.startCode = newStart;
      this.middleCode = getMiddleIndex(char);
    }
  } else {
    // Finish char right now
    this.pushQueue();
    this.reset();
    this.queue += char;
  }
}

HangulIME.prototype.end = function() {
  this.pushQueue();
  this.reset();
}

var ime = new HangulIME();
var sequence = ' xmrtnanswksms akrdlei!!!!!!!';

for(var i = 0; i < sequence.length; ++i) {
  ime.next(sequence.charAt(i));
  console.log(sequence.charAt(i)+' '+ime.queue + '_' + ime.getChar());
}
ime.end();
console.log('$ ' + ime.queue);