# Caesars Cipher Help Help

I am about halfway through with the Casesar’s Cipher puzzle. The Algorithm is incomplete, so disregard the last line of code. What I am wondering is why my

``````for (var i = 0; i < newArray.length; i++) {

unicodeArray.push(newArray[i].charCodeAt());
}

``````

block of code works (I understand I am somehow using a string method on an array)
but this next block of code doesn’t work although very similar.

``````for (var x = 0; x < minus13Array.length; x++) {
newLetterArray.push(minus13Array[x].fromCharCode());
}
``````

I think I can figure the rest of it out if I can figure this one bit out.

``````function rot13(str) { // LBH QVQ VG!
var newArray = str.split("");
var newString = "";
var unicodeArray = [];
var minus13Array = [];
var newLetterArray = [];
for (var i = 0; i < newArray.length; i++) {

unicodeArray.push(newArray[i].charCodeAt());
}
for (var j = 0; j < unicodeArray.length;j++) {
minus13Array.push((unicodeArray[j] - 13));
}
for (var x = 0; x < minus13Array.length; x++) {
newLetterArray.push(minus13Array[x].fromCharCode());
}

return newLetterArray;

}

// Change the inputs below to test
rot13("SERR PBQR PNZC");
``````

Your Browser User Agent is: `Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:54.0) Gecko/20100101 Firefox/54.0.1 Waterfox/54.0.1`.

I can see why you might be confused. If you read the fromCharCode documentation under the Description section, you see that it must always use it in the following way:

``````var numericCode = 65 // ASCII code value for the capital letter 'A'
String.fromCharCode(numericCode) // results in 'A'
``````

The word “String” used above is not arbitrary.’’

However, in the charCodeAt, you can supply your own string like:

``````var myString = 'JavaScript';
myString.charCodeAt();
// the above results in 'J' because if you do not supply an index value for argument,
// the default 0 is used for the index and myString is 'J'
``````

Ahh. I think I understand. So this line of code

``````unicodeArray.push(newArray[i].charCodeAt());
``````

only worked because by default without an argument, the method indexes at , and since [i] iterates only one character at a time, it’s length at all times could be said to be 1? If that is the case I see now why that worked and the second one did not.

Now that you have learned something, what will you do to fix the error you are getting in your code below?

``````newLetterArray.push(minus13Array[x].fromCharCode());
``````

One more thing about using charCodeAt(). The following code is for demonstration purposes only.

``````var myString = 'JavaScript';
for (var i = 0; i < myString.length; i++) {
console.log(myString[i] + ' has code value of ' + myString.charCodeAt(i));
}
``````

Running the above code results in:

J has code value of 74
a has code value of 97
v has code value of 118
a has code value of 97
S has code value of 83
c has code value of 99
r has code value of 114
i has code value of 105
p has code value of 112
t has code value of 116

This is what I have now. I know I’m doing something really dumb.

``````for (var x = 0; x < minus13Array.length; x++) {
newLetterArray.push(minus13Array[x].charCodeAt(minus13Array));
}
``````

Trying to push into a new array. Since charCodeAt() needs indexes as arguments to run, I figured the fully popuated minus13Array would work. Keeps telling me that ‘TypeError: minus13Array[x].charCodeAt is not a function’.

Put the following console.log statement inside the for loop to see what minus13Array[x] is in the first iteration of the loop before the error appears. I think you will be surprised.

``````console.log(minus13Array[x]);
``````

Also the argument that charCodeAt takes should be an index (integer). You are supplying it with minus13Array which is an array.

I added that line in there, but it’s still saying that my code is not a function. I thought it would run the console code first because it came before it. here’s what I have: (also, i decided to try giving it integer arguments, an arbitrary index and length but that produced no change.)

``````for (var x = 0; x < minus13Array.length; x++) {

console.log(minus13Array[x]);
newLetterArray.push(minus13Array.fromCharCode(4,6));
}``````

If I run your code with the console.log statement I mentioned, I get:

``````70
TypeError: minus13Array[x].charCodeAt is not a function
``````

The 70 is the first element in the minus13Array array. 70 is a number and can not use charCodeAt, because it is a String prototype.