Ad:

JavaScript / DHTML / AJAX Discussion Thread
Marked Solved
Views: 10125

Nov 4th, 2009

Regex to remove 'Illegal Characters'

Expand Post »

Hi all

I've been trying to find a regular expression that checks if input contains any of the following characters only:

`~!@#$%^&*()-=+\|/?.>,<;:'"[{]}

I want to allow users to input any normal character a-z or any numbers as well as underscores and any special character that resembles a letter such as é, ê, ô or ÿ etc

So far I have the following which doesn't allow for any of the special characters that I want to allow users to use:

javascript Syntax (Toggle Plain Text)
/[^\w\s]/g
/[^\w\s]/g

The code i'm using is as follows:

javascript Syntax (Toggle Plain Text)
function checkName (strng) {
var error = "";
 
    var illegalChars = /[^\w\s]/g; // allow letters, numbers, and underscores
    if (strng == "") {
   		error = "Please enter your name.\n";
	}
	else if((strng.length < 2)) {
    	error = "The name is the wrong length.\n";
    }
    else if (illegalChars.test(strng)) {
    	error = "The name contains illegal characters.\n";
	}
return error;
}
function checkName (strng) {
var error = "";

    var illegalChars = /[^\w\s]/g; // allow letters, numbers, and underscores
    if (strng == "") {
   		error = "Please enter your name.\n";
	}
	else if((strng.length < 2)) {
    	error = "The name is the wrong length.\n";
    }
    else if (illegalChars.test(strng)) {
    	error = "The name contains illegal characters.\n";
	}
return error;
}

Similar Threads

check string for illegal characters in C#
rename text file by current date in VB.NET
Sending Form in PHP
Remove Non Printing Characters From Text in PHP
Checking for illegal non-numeric characters in JavaScript / DHTML / AJAX

Venom Rush

Reputation Points: 18

Solved Threads: 2

Posting Whiz

Offline

325 posts
since Oct 2007

Permalink

Nov 4th, 2009

Re: Regex to remove 'Illegal Characters'

Try the following character class:
var illegalChars = /[\u0021-\u002f\u003a-\u0040\u005b-\u005e\u0060\u007b-\u007e]/g; // Don't allow any of these Javascript supports specifying unicode characters by hexadecimal expressions like \u0060 and ranges like \u007b-\u007e .

There is a fun website at http://hamstersoup.com/javascript/re...ss_tester.html that gives you the unicode expressions for any character class you specify.

d5e5

Reputation Points: 153

Solved Threads: 142

Master Poster

Offline

740 posts
since Sep 2009

Permalink

Nov 6th, 2009

Re: Regex to remove 'Illegal Characters'

Click to Expand / Collapse Quote originally posted by d5e5 ...

Try the following character class:
var illegalChars = /[\u0021-\u002f\u003a-\u0040\u005b-\u005e\u0060\u007b-\u007e]/g; // Don't allow any of these Javascript supports specifying unicode characters by hexadecimal expressions like \u0060 and ranges like \u007b-\u007e .

There is a fun website at http://hamstersoup.com/javascript/re...ss_tester.html that gives you the unicode expressions for any character class you specify.

Thanks for that but there seems to be one problem...the 'illegal' characters are only detected if they are the first or last letter. If it's anywhere between valid characters it goes undetected. Is there any way I could change the code to fix this?

Venom Rush

Reputation Points: 18

Solved Threads: 2

Posting Whiz

Offline

325 posts
since Oct 2007

Permalink

Nov 6th, 2009

Re: Regex to remove 'Illegal Characters'

Quote ...

...the 'illegal' characters are only detected if they are the first or last letter. If it's anywhere between valid characters it goes undetected.

That's strange, I can't duplicate the problem. Here is the test script I'm using. Can you give me an example to put in the teststring variable that results in undetected illegal characters?

JavaScript / DHTML / AJAX Syntax (Toggle Plain Text)
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
    "http://www.w3.org/TR/html4/strict.dtd"
    >
<html lang="en">
<head>
    <title>Test regex punctuation filter</title>
 
<script type="text/javascript">
function checkName (strng) {
    var error = "";
    var illegalChars = /[\u0021-\u002f\u003a-\u0040\u005b-\u005e\u0060\u007b-\u007e]/g; // Don't allow any of these
    if (strng == "") {
   	error = "Please enter your name.\n";
    }
    else if((strng.length < 2)) {
    	error = "The name is the wrong length.\n";
    }
    else if (illegalChars.test(strng)) {
    	error = "The name contains illegal characters.\n";
    }
return error;
}
 
// The following lines test the function with a string containing illegal chars.
var teststring = "Here is a string with ill:egal ch@racters";
var errmsg = checkName(teststring);
//alert("Testing \'" + teststring + "\' results in \'" + errmsg + "\'");
document.writeln("Testing <p><b>" + teststring + "</b><p> results in <p><b>" + errmsg);
</script>
 
</head>
<body>
 
</body>
</html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
    "http://www.w3.org/TR/html4/strict.dtd"
    >
<html lang="en">
<head>
    <title>Test regex punctuation filter</title>
    
<script type="text/javascript">
function checkName (strng) {
    var error = "";
    var illegalChars = /[\u0021-\u002f\u003a-\u0040\u005b-\u005e\u0060\u007b-\u007e]/g; // Don't allow any of these
    if (strng == "") {
   	error = "Please enter your name.\n";
    }
    else if((strng.length < 2)) {
    	error = "The name is the wrong length.\n";
    }
    else if (illegalChars.test(strng)) {
    	error = "The name contains illegal characters.\n";
    }
return error;
}

// The following lines test the function with a string containing illegal chars.
var teststring = "Here is a string with ill:egal ch@racters";
var errmsg = checkName(teststring);
//alert("Testing \'" + teststring + "\' results in \'" + errmsg + "\'");
document.writeln("Testing <p><b>" + teststring + "</b><p> results in <p><b>" + errmsg);
</script>

</head>
<body>

</body>
</html>

d5e5

Reputation Points: 153

Solved Threads: 142

Master Poster

Offline

740 posts
since Sep 2009

Permalink

Nov 6th, 2009

Simplified my test script

I simplified my test script. It still seems to find illegal characters wherever they are in the test string.

JavaScript / DHTML / AJAX Syntax (Toggle Plain Text)
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
    "http://www.w3.org/TR/html4/strict.dtd"
    >
<html lang="en">
<head>
    <title>Test regex punctuation filter</title>
 
<script type="text/javascript">
function checkString (strng) {
    var error = false;
    var illegalChars = /[\u0021-\u002f\u003a-\u0040\u005b-\u005e\u0060\u007b-\u007e]/g; // Don't allow any of these
    error = (illegalChars.test(strng));
return error;
}
 
// The following lines test the function with a string containing illegal chars.
var teststring = "Here is a str&ing with illegal characters";
var errmsg = checkString(teststring);
document.writeln("Testing \"<b>" + teststring + "</b>\" results in <b>" + errmsg + "</b><p>");
var teststring = "Here is a string without any illegal characters";
var errmsg = checkString(teststring);
document.writeln("Testing \"<b>" + teststring + "</b>\" results in <b>" + errmsg + "</b><p>");
</script>
 
</head>
<body>
</body>
</html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
    "http://www.w3.org/TR/html4/strict.dtd"
    >
<html lang="en">
<head>
    <title>Test regex punctuation filter</title>
    
<script type="text/javascript">
function checkString (strng) {
    var error = false;
    var illegalChars = /[\u0021-\u002f\u003a-\u0040\u005b-\u005e\u0060\u007b-\u007e]/g; // Don't allow any of these
    error = (illegalChars.test(strng));
return error;
}

// The following lines test the function with a string containing illegal chars.
var teststring = "Here is a str&ing with illegal characters";
var errmsg = checkString(teststring);
document.writeln("Testing \"<b>" + teststring + "</b>\" results in <b>" + errmsg + "</b><p>");
var teststring = "Here is a string without any illegal characters";
var errmsg = checkString(teststring);
document.writeln("Testing \"<b>" + teststring + "</b>\" results in <b>" + errmsg + "</b><p>");
</script>

</head>
<body>
</body>
</html>

d5e5

Reputation Points: 153

Solved Threads: 142

Master Poster

Offline

740 posts
since Sep 2009

Permalink

Nov 10th, 2009

Re: Regex to remove 'Illegal Characters'

Click to Expand / Collapse Quote originally posted by d5e5 ...

I simplified my test script. It still seems to find illegal characters wherever they are in the test string.
JavaScript / DHTML / AJAX Syntax (Toggle Plain Text)
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
 "http://www.w3.org/TR/html4/strict.dtd"
 >
<html lang="en">
<head>
 <title>Test regex punctuation filter</title>
 
<script type="text/javascript">
function checkString (strng) {
 var error = false;
 var illegalChars = /[\u0021-\u002f\u003a-\u0040\u005b-\u005e\u0060\u007b-\u007e]/g; // Don't allow any of these
 error = (illegalChars.test(strng));
return error;
}
 
// The following lines test the function with a string containing illegal chars.
var teststring = "Here is a str&ing with illegal characters";
var errmsg = checkString(teststring);
document.writeln("Testing \"" + teststring + "\" results in " + errmsg + "");
var teststring = "Here is a string without any illegal characters";
var errmsg = checkString(teststring);
document.writeln("Testing \"" + teststring + "\" results in " + errmsg + "");
</script>
 
</head>
<body>
</body>
</html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd" > <html lang="en"> <head> <title>Test regex punctuation filter</title> <script type="text/javascript"> function checkString (strng) { var error = false; var illegalChars = /[\u0021-\u002f\u003a-\u0040\u005b-\u005e\u0060\u007b-\u007e]/g; // Don't allow any of these error = (illegalChars.test(strng)); return error; } // The following lines test the function with a string containing illegal chars. var teststring = "Here is a str&ing with illegal characters"; var errmsg = checkString(teststring); document.writeln("Testing \"" + teststring + "\" results in " + errmsg + ""); var teststring = "Here is a string without any illegal characters"; var errmsg = checkString(teststring); document.writeln("Testing \"" + teststring + "\" results in " + errmsg + ""); </script> </head> <body> </body> </html>

Strange, try using one word in your test with an illegal character in the middle of the word. That's what I've been testing and it only detects the illegal character at the start or end of the word

Venom Rush

Reputation Points: 18

Solved Threads: 2

Posting Whiz

Offline

325 posts
since Oct 2007

Permalink

Nov 10th, 2009

Remove the /g modifier

In that regex for illegal characters I should not have put the \g modifier at the end. As soon as we find the first illegal character that is all we need to know. The /g global modifier attempts to match all illegal characters in the string starting at the position where it previously found a match. All we need to know is whether there is at least one illegal character in the string so we don't need /g and it is somehow giving us inconsistent results.

In your script, try replacing the regex like this:

JavaScript / DHTML / AJAX Syntax (Toggle Plain Text)
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
    "http://www.w3.org/TR/html4/strict.dtd"
    >
<html lang="en">
<head>
    <title>Test regex punctuation filter</title>
 
<script type="text/javascript">
function checkString (strng) {
    var error = false;
//var illegalChars = /[\u0021-\u002f\u003a-\u0040\u005b-\u005e\u0060\u007b-\u007e]/g; // The /g (for global) is a goof.
    var illegalChars = /[\u0021-\u002f\u003a-\u0040\u005b-\u005e\u0060\u007b-\u007e]/; // NOT global.
    error = (illegalChars.test(strng));
return error;
}
 
// The following lines test the function with a string containing illegal chars.
var teststring = "Java$cript"; //Illegal character. Test should return 'true'
var errmsg = checkString(teststring);
document.writeln("Testing \"<b>" + teststring + "</b>\" results in <b>" + errmsg + "</b><p>");
var teststring = "Javascript"; //No illegal character. Test should return 'false'
var errmsg = checkString(teststring);
document.writeln("Testing \"<b>" + teststring + "</b>\" results in <b>" + errmsg + "</b><p>");
</script>
 
</head>
<body>
 
</body>
</html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
    "http://www.w3.org/TR/html4/strict.dtd"
    >
<html lang="en">
<head>
    <title>Test regex punctuation filter</title>
    
<script type="text/javascript">
function checkString (strng) {
    var error = false;
//var illegalChars = /[\u0021-\u002f\u003a-\u0040\u005b-\u005e\u0060\u007b-\u007e]/g; // The /g (for global) is a goof.
    var illegalChars = /[\u0021-\u002f\u003a-\u0040\u005b-\u005e\u0060\u007b-\u007e]/; // NOT global.
    error = (illegalChars.test(strng));
return error;
}

// The following lines test the function with a string containing illegal chars.
var teststring = "Java$cript"; //Illegal character. Test should return 'true'
var errmsg = checkString(teststring);
document.writeln("Testing \"<b>" + teststring + "</b>\" results in <b>" + errmsg + "</b><p>");
var teststring = "Javascript"; //No illegal character. Test should return 'false'
var errmsg = checkString(teststring);
document.writeln("Testing \"<b>" + teststring + "</b>\" results in <b>" + errmsg + "</b><p>");
</script>

</head>
<body>

</body>
</html>

d5e5

Reputation Points: 153

Solved Threads: 142

Master Poster

Offline

740 posts
since Sep 2009

Permalink

Nov 11th, 2009

Re: Regex to remove 'Illegal Characters'

Perfect. Thanks for that d5e5. Works exactly the way I want now.

Venom Rush

Reputation Points: 18

Solved Threads: 2

Posting Whiz

Offline

325 posts
since Oct 2007

This thread is solved

Either the thread starter or a moderator has marked this thread as solved. You can most likely trust the responses and answers given. There is most likely no reason for any further responses to be posted here. If you have a related question, please start a new thread in this forum instead.

This thread is more than three months old

No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.

Previous Thread in JavaScript / DHTML / AJAX Forum Timeline: HELP! to autoplay or setinterval to YUI carousel

Next Thread in JavaScript / DHTML / AJAX Forum Timeline: how to show a larger input field with mouseover?

DaniWeb Message

Cancel Changes

User Name
Password