Problem with caesar cipher shift javascript

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For a school project, I'm trying to create a website on encryption methods, but right now I have a problem with my Caesar one. I checked so many times but I can't find out where is the problem in my code. I think the shift is what is wrong, but I don't know what I could change to make it work, and I would be very happy if someone could help me.

So, here is the html part :

<form name="formu" action="">

<label for="pseudo">Your text :</label>

<br>

<textarea name="text" id="text_encode" style="width: 30%;height: 200px"> 

</textarea>

<br>

<br>



<label for="methods">Select your methods : </label>

<br>

<br>

<select name="methods" id="methods">



  <option value="Caesar">Caesar</option>





</select>

<br>

<br>

<input type="button" value="Encrypt" onClick=encryption()>





<br>

<br>

<textarea name="text" id="text_decoded" style="width: 30%;height: 200px" 

readonly="readonly"></textarea>

</form>

And here is my javascript code:

function encryption() {    

switch(document.getElementById("methods").value) {

    case "Caesar":

        var str = document.getElementById("text_encode").value;

        var amount = prompt("Number of shift");

        var output = "";



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

            var c = str[i];

            var code = str.charCodeAt(i);



            if ((code >= 65) && (code <= 90))

                c = String.fromCharCode(((code - 65 + amount) % 26) + 65);

            else if ( (code >= 97) && (code <= 122) )

                c = String.fromCharCode(((code - 97 + amount) % 26) + 97);



            output += c;

        }

        document.getElementById("text_decoded").value=output;

        break;

    }

}

You can also go here if you want to test what's wrong directly: https://www.w3schools.com/code/tryit.asp?filename=FXJU1NAG37C0

edited Mar 8 at 1:25

Jack Bashford

17.8k51949

asked Nov 24 '18 at 20:51

Hatu7

So what is the problem? Please edit your question. What happens when you run your code? What did you expect to happen instead?

– Robert
Nov 24 '18 at 21:34

add a comment |

So, here is the html part :

<form name="formu" action="">

<label for="pseudo">Your text :</label>

<br>

<textarea name="text" id="text_encode" style="width: 30%;height: 200px"> 

</textarea>

<br>

<br>



<label for="methods">Select your methods : </label>

<br>

<br>

<select name="methods" id="methods">



  <option value="Caesar">Caesar</option>





</select>

<br>

<br>

<input type="button" value="Encrypt" onClick=encryption()>





<br>

<br>

<textarea name="text" id="text_decoded" style="width: 30%;height: 200px" 

readonly="readonly"></textarea>

</form>

And here is my javascript code:

function encryption() {    

switch(document.getElementById("methods").value) {

    case "Caesar":

        var str = document.getElementById("text_encode").value;

        var amount = prompt("Number of shift");

        var output = "";



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

            var c = str[i];

            var code = str.charCodeAt(i);



            if ((code >= 65) && (code <= 90))

                c = String.fromCharCode(((code - 65 + amount) % 26) + 65);

            else if ( (code >= 97) && (code <= 122) )

                c = String.fromCharCode(((code - 97 + amount) % 26) + 97);



            output += c;

        }

        document.getElementById("text_decoded").value=output;

        break;

    }

}

You can also go here if you want to test what's wrong directly: https://www.w3schools.com/code/tryit.asp?filename=FXJU1NAG37C0

edited Mar 8 at 1:25

Jack Bashford

17.8k51949

asked Nov 24 '18 at 20:51

Hatu7

So what is the problem? Please edit your question. What happens when you run your code? What did you expect to happen instead?

– Robert
Nov 24 '18 at 21:34

add a comment |

So, here is the html part :

<form name="formu" action="">

<label for="pseudo">Your text :</label>

<br>

<textarea name="text" id="text_encode" style="width: 30%;height: 200px"> 

</textarea>

<br>

<br>



<label for="methods">Select your methods : </label>

<br>

<br>

<select name="methods" id="methods">



  <option value="Caesar">Caesar</option>





</select>

<br>

<br>

<input type="button" value="Encrypt" onClick=encryption()>





<br>

<br>

<textarea name="text" id="text_decoded" style="width: 30%;height: 200px" 

readonly="readonly"></textarea>

</form>

And here is my javascript code:

function encryption() {    

switch(document.getElementById("methods").value) {

    case "Caesar":

        var str = document.getElementById("text_encode").value;

        var amount = prompt("Number of shift");

        var output = "";



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

            var c = str[i];

            var code = str.charCodeAt(i);



            if ((code >= 65) && (code <= 90))

                c = String.fromCharCode(((code - 65 + amount) % 26) + 65);

            else if ( (code >= 97) && (code <= 122) )

                c = String.fromCharCode(((code - 97 + amount) % 26) + 97);



            output += c;

        }

        document.getElementById("text_decoded").value=output;

        break;

    }

}

You can also go here if you want to test what's wrong directly: https://www.w3schools.com/code/tryit.asp?filename=FXJU1NAG37C0

edited Mar 8 at 1:25

Jack Bashford

17.8k51949

asked Nov 24 '18 at 20:51

Hatu7

So, here is the html part :

<form name="formu" action="">

<label for="pseudo">Your text :</label>

<br>

<textarea name="text" id="text_encode" style="width: 30%;height: 200px"> 

</textarea>

<br>

<br>



<label for="methods">Select your methods : </label>

<br>

<br>

<select name="methods" id="methods">



  <option value="Caesar">Caesar</option>





</select>

<br>

<br>

<input type="button" value="Encrypt" onClick=encryption()>





<br>

<br>

<textarea name="text" id="text_decoded" style="width: 30%;height: 200px" 

readonly="readonly"></textarea>

</form>

And here is my javascript code:

function encryption() {    

switch(document.getElementById("methods").value) {

    case "Caesar":

        var str = document.getElementById("text_encode").value;

        var amount = prompt("Number of shift");

        var output = "";



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

            var c = str[i];

            var code = str.charCodeAt(i);



            if ((code >= 65) && (code <= 90))

                c = String.fromCharCode(((code - 65 + amount) % 26) + 65);

            else if ( (code >= 97) && (code <= 122) )

                c = String.fromCharCode(((code - 97 + amount) % 26) + 97);



            output += c;

        }

        document.getElementById("text_decoded").value=output;

        break;

    }

}

You can also go here if you want to test what's wrong directly: https://www.w3schools.com/code/tryit.asp?filename=FXJU1NAG37C0

javascript jquery html string encryption

edited Mar 8 at 1:25

Jack Bashford

17.8k51949

asked Nov 24 '18 at 20:51

Hatu7

edited Mar 8 at 1:25

Jack Bashford

17.8k51949

asked Nov 24 '18 at 20:51

Hatu7

edited Mar 8 at 1:25

Jack Bashford

17.8k51949

edited Mar 8 at 1:25

Jack Bashford

17.8k51949

edited Mar 8 at 1:25

Jack Bashford

17.8k51949

asked Nov 24 '18 at 20:51

Hatu7

asked Nov 24 '18 at 20:51

Hatu7

asked Nov 24 '18 at 20:51

Hatu7

So what is the problem? Please edit your question. What happens when you run your code? What did you expect to happen instead?

– Robert
Nov 24 '18 at 21:34

add a comment |

So what is the problem? Please edit your question. What happens when you run your code? What did you expect to happen instead?

– Robert
Nov 24 '18 at 21:34

So what is the problem? Please edit your question. What happens when you run your code? What did you expect to happen instead?

– Robert
Nov 24 '18 at 21:34

add a comment |

1 Answer
1

active

oldest

votes

The mistake is this line:

var amount = prompt("Number of shift");

This by default returns a string, but it may contain a number - so if I enter 10 in the prompt box, amount will be:

amount = "10"

To fix this, you need to parse the string into an integer:

var amount = Number(prompt("Number of shift"));

Then your code should work.

answered Nov 24 '18 at 21:04

Jack Bashford

17.8k51949

Thanks! I thought that if I entered a number, It would correctly recognize even as a string, but I guess I'm going to need to be more careful next time.

– Hatu7
Nov 24 '18 at 21:08

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

The mistake is this line:

var amount = prompt("Number of shift");

This by default returns a string, but it may contain a number - so if I enter 10 in the prompt box, amount will be:

amount = "10"

To fix this, you need to parse the string into an integer:

var amount = Number(prompt("Number of shift"));

Then your code should work.

answered Nov 24 '18 at 21:04

Jack Bashford

17.8k51949

Thanks! I thought that if I entered a number, It would correctly recognize even as a string, but I guess I'm going to need to be more careful next time.

– Hatu7
Nov 24 '18 at 21:08

add a comment |

The mistake is this line:

var amount = prompt("Number of shift");

This by default returns a string, but it may contain a number - so if I enter 10 in the prompt box, amount will be:

amount = "10"

To fix this, you need to parse the string into an integer:

var amount = Number(prompt("Number of shift"));

Then your code should work.

answered Nov 24 '18 at 21:04

Jack Bashford

17.8k51949

Thanks! I thought that if I entered a number, It would correctly recognize even as a string, but I guess I'm going to need to be more careful next time.

– Hatu7
Nov 24 '18 at 21:08

add a comment |

The mistake is this line:

var amount = prompt("Number of shift");

This by default returns a string, but it may contain a number - so if I enter 10 in the prompt box, amount will be:

amount = "10"

To fix this, you need to parse the string into an integer:

var amount = Number(prompt("Number of shift"));

Then your code should work.

answered Nov 24 '18 at 21:04

Jack Bashford

17.8k51949

The mistake is this line:

var amount = prompt("Number of shift");

This by default returns a string, but it may contain a number - so if I enter 10 in the prompt box, amount will be:

amount = "10"

To fix this, you need to parse the string into an integer:

var amount = Number(prompt("Number of shift"));

Then your code should work.

answered Nov 24 '18 at 21:04

Jack Bashford

17.8k51949

answered Nov 24 '18 at 21:04

Jack Bashford

17.8k51949

answered Nov 24 '18 at 21:04

Jack Bashford

17.8k51949

answered Nov 24 '18 at 21:04

Jack Bashford

17.8k51949

Thanks! I thought that if I entered a number, It would correctly recognize even as a string, but I guess I'm going to need to be more careful next time.

– Hatu7
Nov 24 '18 at 21:08

add a comment |

Thanks! I thought that if I entered a number, It would correctly recognize even as a string, but I guess I'm going to need to be more careful next time.

– Hatu7
Nov 24 '18 at 21:08

Thanks! I thought that if I entered a number, It would correctly recognize even as a string, but I guess I'm going to need to be more careful next time.

– Hatu7
Nov 24 '18 at 21:08

add a comment |

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