function levenshtein (s1, s2) {
      // Calculate Levenshtein distance between two strings  
    // 
    // version: 909.322
    // discuss at: http://phpjs.org/functions/levenshtein      // +            original by: Carlos R. L. Rodrigues (http://www.jsfromhell.com)
      // +            bugfixed by: Onno Marsman
      // +             revised by: Andrea Giammarchi (http://webreflection.blogspot.com)
      // + reimplemented by: Brett Zamir (http://brett-zamir.me)
      // + reimplemented by: Alexander M Beedie      // *                example 1: levenshtein('Kevin van Zonneveld', 'Kevin van Sommeveld');
      // *                returns 1: 3
    if (s1 == s2) {
        return 0;
    } 
    var s1_len = s1.length;
    var s2_len = s2.length;
    if (s1_len === 0) {
        return s2_len;    }
    if (s2_len === 0) {
        return s1_len;
    }
     // BEGIN STATIC
    var split = false;
    try{
        split=!('0')[0];
    } catch (e){        split=true; // Earlier IE may not support access by string index
    }
    // END STATIC
    if (split){
        s1 = s1.split('');        s2 = s2.split('');
    }
 
    var v0 = new Array(s1_len+1);
    var v1 = new Array(s1_len+1); 
    var s1_idx=0, s2_idx=0, cost=0;
    for (s1_idx=0; s1_idx<s1_len+1; s1_idx++) {
        v0[s1_idx] = s1_idx;
    }    var char_s1='', char_s2='';
    for (s2_idx=1; s2_idx<=s2_len; s2_idx++) {
        v1[0] = s2_idx;
        char_s2 = s2[s2_idx - 1];
         for (s1_idx=0; s1_idx<s1_len;s1_idx++) {
            char_s1 = s1[s1_idx];
            cost = (char_s1 == char_s2) ? 0 : 1;
            var m_min = v0[s1_idx+1] + 1;
            var b = v1[s1_idx] + 1;            var c = v0[s1_idx] + cost;
            if (b < m_min) {
                m_min = b; }
            if (c < m_min) {
                m_min = c; }            v1[s1_idx+1] = m_min;
        }
        var v_tmp = v0;
        v0 = v1;
        v1 = v_tmp;    }
    return v0[s1_len];
}