How to block special characters?
Question
I want to block special character in this code. In other words, user can enter only alphanumeric value and use backspace for delete.
Bug : when I wrote code==8 in if condition then it allow all special characters.
<html>
<head>
<title>practice</title>
<script type="text/javascript">
function noSpecialChar(e){
if (e.keyCode)
code = e.keyCode;
else if (e.which)
code = e.which;
//code==8 => backspace
//(code>=65 && code<=90) => alphabets
//(code>=48 && code<=57) => numeric
if((code>=65 && code<=90)||(code>=48&&code<=57)||(code==8)){
return true;
}else{
return false;
}
}
</script>
</head>
<body>
<input type="text" name="txtName" id="txtName" onkeydown=" return noSpecialChar(window.event);"/>
</body>
</html>
2 answers
solution1
1 ACCPTED 2012-03-26 05:29:33
Doing such filtering properly is tricky. The following example uses the code in "JavaScript: The Definitive Guide", section "17.8 Text Events". If you wish to use it, download the code from the O'Reilly server instead of directly referring to it in your code. The code uses the whenReady.js routine which you can download from https://github.com/kukawski/whenReady/blob/master/whenReady.js
<!doctype html>
<script src="whenReady.js"></script>
<script src=
"http://examples.oreilly.com/9780596805531/examples/17.06.InputFilter.js">
</script>
<label for="txtName">Text:</label><input id="txtName" type="text"
data-allowed-chars=
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
data-messageid="input-error">
<span id="input-error" style="color:red;visibility:hidden">Alphanumeric
characters only</span>
It might be slightly better to modify the code so that instead of a data- attribute, it uses a pattern attribute, which would give some functionality on some browsers even when JavaScript is disabled, as well as flexibility in specifying the set of allowed characters. But then you would need to effectively implement a regular expression parser, so the gain might not correspond to the work needed.
solution2
0 2014-05-25 12:05:02
I have a script for which characters are allowed:
Consider your html: <input type="text" id="yourID"></input>
<script>
document.getElementById("yourID").onkeypress = function(e) {
var chr = String.fromCharCode(e.which);
if ("Which characters are allowed? Type them instead of these, without any seperation".indexOf(chr) < 0)
return false;
};
</script>
If you want do allow only letters and numbers use this:
<script>
document.getElementById("yourID").onkeypress = function(e) {
var chr = String.fromCharCode(e.which);
if ("1234567890qwertyuioplkjhgfdsazxcvbnmQWERTYUIOPLKJHGFDSAZXCVBNM".indexOf(chr) < 0)
return false;
};
</script>
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