cesar cryptography

// cesar encrypt

var msg = "quisieraquelaclaseseatemprano";
var letters = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","ñ","o","p","q","r","s","t","u","v","w","x","y","z" ];
var a = 3;
var b = 5;
var result = []
for (var i = 0; i < msg.length ; i ++){
  for(var j = 0; j < letters.length ; j ++) {
      if(msg[i] == letters[j]) { var p=((j*a+b) % 27 ); result.push(letters[p]); }
    }
}

// cesar cryptanalysis


//var msg = "chvwhhvxpexhphmhuflflrsdudgvfliudd"
var msg = "qgkzñigkyvxñruxjñgqvgxgykxashaksvulkyñusgq"
var letters=["a","b","c","d","e","f","g","h","i","j","k","l","m","n","ñ","o","p","q","r","s","t","u","v","w","x","y","z" ];
var count = {}
for (var i = 0; i < msg.length ; i++ ){
    if ( msg[i] in count ) { count[msg[i]] = count[msg[i]] +1 } else { count[msg[i]] = 1 }
}
var sortable = [];
for (var vehicle in count)
    sortable.push([vehicle, count [vehicle]])
var ordered = sortable.sort(function(a, b) {return a[1] - b[1]})
        
var len = ordered.length
var last = ordered[len-1]
var unlast = ordered[len-2]

var a = 0
var e = 4
var b1 = 0
var b2 = 0

for (var j=0; j<letters.length;j++ ){
    if(letters[j]==last[0]) { b1 = j - e};
}
for (var j=0; j<letters.length;j++ ){
    if(letters[j]==unlast[0]) { b2 = j - a};
}
    if ( b1 != b2 ) {
    for (var j=0; j<letters.length;j++ ){
        if(letters[j]==last[0]) { b1 = j - a};
    }
    for (var j=0; j<letters.length;j++ ){
        if(letters[j]==unlast[0]) { b2 = j - e};
    }
    }
        
var result = []
for (var i = 0; i < msg.length ; i ++){
  for(var j = 0; j < letters.length ; j ++) {
      if(msg[i] == letters[j]) { var p=((j-b1+27) % 27 ); result.push(letters[p]);}
    }
}
alert(result)