Having problems using fromCharCode() and charCodeAt() for use in an encrypter

czarcalvinsk · 01-01-2012, 04:12 PM

I am creating a encrypting program, which changes the ASCII value of the characters by 78 then outputting them as an alert. However, the alert isn't popping up.
I believe the problem lies in the second for loop where the fromCharCode() and getCharAt() are used.

Here is the HTML code

Code:

<!doctype html>
<html lang="en">
<head>
	<meta charset="utf-8" />
	<script src="encrypt.js"></script>
	<script src="decrypt.js"></script>
<title>Encrypter/Decrypter</title>
</head>
<body>
	<div id="big_wrapper">
		<p id="encrypt">Encrypt</p>
		<input type="button" value="Click to Encrypt" name="encrypt" onClick="getTxt()">
		<p id="decrypt">Decrypt</p>
	</div>
</body>
</html>

Here is the Javascript code:

Code:

function getTxt(){
	var x=prompt("Enter the text you want to encrypt");
	alert(encrypt(x));
}
function setCharAt(str,index,chr) {
	if(index > str.length-1) return str;
	return str.substr(0,index) + chr + str.substr(index+1);
}

function encrypt(text){

	var i =0;	//preparing all of the variables
	var cryptarray = new Array();
	for (i=0;i<1000;i++){
		cryptarray[i]=null;
	}
	
	for (i=0;i<text.length;i++){
		 cryptarray[i]=text.fromCharCode((text.charCodeAt(i)+78)) //loops through the string, taking characters and adding 78 to their ascii value and putting them in the temp array
	}
	
	var temptext = text;
	for (i=0;i<text.length;i++){
		temptext.setCharAt(i)=cryptarray[i];	//converts the array into a string
	}
	return temptext;
}

DaveyErwin · 01-01-2012, 05:18 PM

Code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<meta name="generator" content="daveyerwin">
<title>Untitled</title>
<script type="text/javascript">

function getTxt(){
	var x=prompt("Enter the text you want to encrypt");
	alert(encrypt(x));
}
function setCharAt(str,index,chr) {
	if(index > str.length-1) return str;
	return str.substr(0,index) + chr + str.substr(index+1);
}
function encrypt(text){
	var i =0;	//preparing all of the variables
	var cryptarray = new Array();
	for (i=0;i<1000;i++){
		cryptarray[i]=null;
	}	
	for (i=0;i<text.length;i++){
		 cryptarray[i]=String.fromCharCode((text.charCodeAt(i)+78)) //loops through the string, taking characters and adding 78 to their ascii value and putting them in the temp array
	}	
	var temptext = text;	
		temptext=cryptarray.join("");	//converts the array into a string	
	return temptext;
}
</script>
</head>
<body>
	<div id="big_wrapper">
		<p id="encrypt">Encrypt</p>
		<input type="button" value="Click to Encrypt" name="encrypt" onClick="getTxt()">
		<p id="decrypt">Decrypt</p>
	</div>
</body>
</html>

jmrker · 01-02-2012, 03:54 AM

I assume you want to decrypt as well...

Code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<meta name="generator" content="daveyerwin">
<title>Untitled</title>
<script type="text/javascript">
// From: http://www.codingforums.com/showthread.php?p=1176065#post1176065

function getTxt(){
  var x=document.getElementById('inTxt').value;
  document.getElementById('outTxt').value = encrypt(x);
}
function putTxt(){
  var x=document.getElementById('outTxt').value;
  document.getElementById('inTxt').value = decrypt(x);
}
function setCharAt(str,index,chr) {
  if(index > str.length-1) return str;
  return str.substr(0,index) + chr + str.substr(index+1);
}
function encrypt(text){
  var i =0;	//preparing all of the variables
  var cryptarray = [];
  for (i=0;i<text.length;i++){
    cryptarray.push(String.fromCharCode((text.charCodeAt(i)+78)));
// loops through the string, taking characters and adding 78 to their ascii value
// and putting them in the temp array
  }	
  var temptext = text;	
  temptext=cryptarray.join("");	//converts the array into a string	
  return temptext;
}

function decrypt(text){
  var i =0;	//preparing all of the variables
  var cryptarray = [];
  for (i=0;i<text.length;i++){
    cryptarray.push(String.fromCharCode((text.charCodeAt(i)-78)));
// loops through the string, taking characters and subtracting 78 to their ascii value
// and putting them in the temp array
  }	
  var temptext = text;	
  temptext=cryptarray.join("");	//converts the array into a string	
  return temptext;
}

</script>
</head>
<body>
 <div id="big_wrapper">
  <p id="encrypt">Encrypt</p>
  <input type="text" id="inTxt" value="Now is the time 4 all">
  <input type="button" value="Click to Encrypt" name="encrypt" onClick="getTxt()">
  <button onclick="document.getElementById('inTxt').value = ''">Clear</button>

  <p id="decrypt">Decrypt</p>
  <input type="text" id="outTxt" value="">
  <input type="button" value="Click to Decrypt" name="encrypt" onClick="putTxt()">
  <button onclick="document.getElementById('outTxt').value = ''">Clear</button>
 </div>
</body>
</html>

Also, there is no 1000 character limit with this method.

You could also combine the encrypt/decrypt functions into one single function.

jmrker · 01-02-2012, 03:59 AM

Combined encryption/decryption ...

Code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
 "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<meta name="generator" content="daveyerwin">
<title>Untitled</title>
<script type="text/javascript">
// From: http://www.codingforums.com/showthread.php?p=1176065#post1176065

function getTxt(){
  var x=document.getElementById('inTxt').value;
  document.getElementById('outTxt').value = crypt(x,true);
}
function putTxt(){
  var x=document.getElementById('outTxt').value;
  document.getElementById('inTxt').value = crypt(x,false);
}
function setCharAt(str,index,chr) {
  if(index > str.length-1) return str;
  return str.substr(0,index) + chr + str.substr(index+1);
}
function crypt(text,flag){
  var i =0;	//preparing all of the variables
  var cryptarray = [];
  for (i=0;i<text.length;i++){
    if (flag) {
      cryptarray.push(String.fromCharCode((text.charCodeAt(i)+78)));
// loops through the string, taking characters and adding 78 to their ascii value
// and putting them in the temp array
    } else {
      cryptarray.push(String.fromCharCode((text.charCodeAt(i)-78)));
// loops through the string, taking characters and subtracting 78 to their ascii value
// and putting them in the temp array
    }
  }	
  var temptext = text;	
  temptext=cryptarray.join("");	//converts the array into a string	
  return temptext;
}

</script>
</head>
<body>
 <div id="big_wrapper">
  <p id="encrypt">Encrypt</p>
  <input type="text" id="inTxt" value="Now is the time 4 all">
  <input type="button" value="Click to Encrypt" name="encrypt" onClick="getTxt()">
  <button onclick="document.getElementById('inTxt').value = ''">Clear</button>

  <p id="decrypt">Decrypt</p>
  <input type="text" id="outTxt" value="">
  <input type="button" value="Click to Decrypt" name="encrypt" onClick="putTxt()">
  <button onclick="document.getElementById('outTxt').value = ''">Clear</button>
 </div>
</body>
</html>