how do i block or restrict special characters from input fields with jquery?

Question

How do I block special characters from being typed into an input field with jquery?

Answer 1

A simple example using a regular expression which you could change to allow/disallow whatever you like.

$('input').on('keypress', function (event) {
    var regex = new RegExp("^[a-zA-Z0-9]+$");
    var key = String.fromCharCode(!event.charCode ? event.which : event.charCode);
    if (!regex.test(key)) {
       event.preventDefault();
       return false;
    }
});

Answer 2

I was looking for an answer that restricted input to only alphanumeric characters, but still allowed for the use of control characters (e.g., backspace, delete, tab) and copy+paste. None of the provided answers that I tried satisfied all of these requirements, so I came up with the following using the input event.

$('input').on('input', function() {
  $(this).val($(this).val().replace(/[^a-z0-9]/gi, ''));
});

Edit:
As rinogo pointed out in the comments, the above code snippet forces the cursor to the end of the input when typing in the middle of the input text. I believe the code snippet below solves this problem.

$('input').on('input', function() {
  var c = this.selectionStart,
      r = /[^a-z0-9]/gi,
      v = $(this).val();
  if(r.test(v)) {
    $(this).val(v.replace(r, ''));
    c--;
  }
  this.setSelectionRange(c, c);
});

Answer 3

Short answer: prevent the 'keypress' event:

$("input").keypress(function(e){
    var charCode = !e.charCode ? e.which : e.charCode;

    if(/* Test for special character */ )
        e.preventDefault();
})

Long answer: Use a plugin like jquery.alphanum

There are several things to consider when picking a solution:

• Pasted text
• Control characters like backspace or F5 may be prevented by the above code.
• é, í, ä etc
• Arabic or Chinese...
• Cross Browser compatibility

I think this area is complex enough to warrant using a 3rd party plugin. I tried out several of the available plugins but found some problems with each of them so I went ahead and wrote jquery.alphanum. The code looks like this:

$("input").alphanum();

Or for more fine-grained control, add some settings:

$("#username").alphanum({
    allow      : "€$£",
    disallow   : "xyz",
    allowUpper : false
});

Hope it helps.

Answer 4

Use HTML5's pattern input attribute!

<input type="text" pattern="^[a-zA-Z0-9]+$" />

Answer 5

Take a look at the jQuery alphanumeric plugin. https://github.com/KevinSheedy/jquery.alphanum

//All of these are from their demo page
//only numbers and alpha characters
$('.sample1').alphanumeric();
//only numeric
$('.sample4').numeric();
//only numeric and the .
$('.sample5').numeric({allow:"."});
//all alphanumeric except the . 1 and a
$('.sample6').alphanumeric({ichars:'.1a'});

Answer 6

Use regex to allow/disallow anything. Also, for a slightly more robust version than the accepted answer, allowing characters that don't have a key value associated with them (backspace, tab, arrow keys, delete, etc.) can be done by first passing through the keypress event and check the key based on keycode instead of value.

$('#input').bind('keydown', function (event) {
        switch (event.keyCode) {
            case 8:  // Backspace
            case 9:  // Tab
            case 13: // Enter
            case 37: // Left
            case 38: // Up
            case 39: // Right
            case 40: // Down
            break;
            default:
            var regex = new RegExp("^[a-zA-Z0-9.,/ $@()]+$");
            var key = event.key;
            if (!regex.test(key)) {
                event.preventDefault();
                return false;
            }
            break;
        }
});

Answer 7

Your textbox:

<input type="text" id="name">

Your javascript:

$("#name").keypress(function(event) {
    var character = String.fromCharCode(event.keyCode);
    return isValid(character);     
});

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

Answer 8

Write some javascript code on onkeypress event of textbox. as per requirement allow and restrict character in your textbox

function isNumberKeyWithStar(evt) {
    var charCode = (evt.which) ? evt.which : event.keyCode
    if (charCode > 31 && (charCode < 48 || charCode > 57) && charCode != 42)
        return false;
    return true;
}
function isNumberKey(evt) {
    var charCode = (evt.which) ? evt.which : event.keyCode
    if (charCode > 31 && (charCode < 48 || charCode > 57))
        return false;
    return true;
}
function isNumberKeyForAmount(evt) {
    var charCode = (evt.which) ? evt.which : event.keyCode
    if (charCode > 31 && (charCode < 48 || charCode > 57) && charCode != 46)
        return false;
    return true;
}

Answer 9

I use this code modifying others that I saw. Only grand to the user write if the key pressed or pasted text pass the pattern test (match) (this example is a text input that only allows 8 digits)

$("input").on("keypress paste", function(e){
    var c = this.selectionStart, v = $(this).val();
    if (e.type == "keypress")
        var key = String.fromCharCode(!e.charCode ? e.which : e.charCode)
    else
        var key = e.originalEvent.clipboardData.getData('Text')
    var val = v.substr(0, c) + key + v.substr(c, v.length)
    if (!val.match(/\d{0,8}/) || val.match(/\d{0,8}/).toString() != val) {
        e.preventDefault()
        return false
    }
})

Answer 10

this is an example that prevent the user from typing the character "a"

$(function() {
$('input:text').keydown(function(e) {
if(e.keyCode==65)
    return false;

});
});

key codes refrence here:
http://www.expandinghead.net/keycode.html

Answer 11

Yes you can do by using jQuery as:

<script>
$(document).ready(function()
{
    $("#username").blur(function()
    {
        //remove all the class add the messagebox classes and start fading
        $("#msgbox").removeClass().addClass('messagebox').text('Checking...').fadeIn("slow");
        //check the username exists or not from ajax
        $.post("user_availability.php",{ user_name:$(this).val() } ,function(data)
        {
          if(data=='empty') // if username is empty
          {
            $("#msgbox").fadeTo(200,0.1,function() //start fading the messagebox
            { 
              //add message and change the class of the box and start fading
              $(this).html('Empty user id is not allowed').addClass('messageboxerror').fadeTo(900,1);
            });
          }
          else if(data=='invalid') // if special characters used in username
          {
            $("#msgbox").fadeTo(200,0.1,function() //start fading the messagebox
            { 
              //add message and change the class of the box and start fading
              $(this).html('Sorry, only letters (a-z), numbers (0-9), and periods (.) are allowed.').addClass('messageboxerror').fadeTo(900,1);
            });
          }
          else if(data=='no') // if username not avaiable
          {
            $("#msgbox").fadeTo(200,0.1,function() //start fading the messagebox
            { 
              //add message and change the class of the box and start fading
              $(this).html('User id already exists').addClass('messageboxerror').fadeTo(900,1);
            });     
          }
          else
          {
            $("#msgbox").fadeTo(200,0.1,function()  //start fading the messagebox
            { 
              //add message and change the class of the box and start fading
              $(this).html('User id available to register').addClass('messageboxok').fadeTo(900,1); 
            });
          }

        });

    });
});
</script>
<input type="text" id="username" name="username"/><span id="msgbox" style="display:none"></span>

and script for your user_availability.php will be:

<?php
include'includes/config.php';

//value got from the get method
$user_name = trim($_POST['user_name']);

if($user_name == ''){
    echo "empty";
}elseif(preg_match('/[\'^£$%&*()}{@#~?><>,|=_+¬-]/', $user_name)){
    echo "invalid";
}else{
    $select = mysql_query("SELECT user_id FROM staff");

    $i=0;
    //this varible contains the array of existing users
    while($fetch = mysql_fetch_array($select)){
        $existing_users[$i] = $fetch['user_id'];
        $i++;
    }

    //checking weather user exists or not in $existing_users array
    if (in_array($user_name, $existing_users))
    {
        //user name is not availble
        echo "no";
    } 
    else
    {
        //user name is available
        echo "yes";
    }
}
?>

I tried to add for / and \ but not succeeded.

---

You can also do it by using javascript & code will be:

<!-- Check special characters in username start -->
<script language="javascript" type="text/javascript">
function check(e) {
    var keynum
    var keychar
    var numcheck
    // For Internet Explorer
    if (window.event) {
        keynum = e.keyCode;
    }
    // For Netscape/Firefox/Opera
    else if (e.which) {
        keynum = e.which;
    }
    keychar = String.fromCharCode(keynum);
    //List of special characters you want to restrict
    if (keychar == "'" || keychar == "`" || keychar =="!" || keychar =="@" || keychar =="#" || keychar =="$" || keychar =="%" || keychar =="^" || keychar =="&" || keychar =="*" || keychar =="(" || keychar ==")" || keychar =="-" || keychar =="_" || keychar =="+" || keychar =="=" || keychar =="/" || keychar =="~" || keychar =="<" || keychar ==">" || keychar =="," || keychar ==";" || keychar ==":" || keychar =="|" || keychar =="?" || keychar =="{" || keychar =="}" || keychar =="[" || keychar =="]" || keychar =="¬" || keychar =="£" || keychar =='"' || keychar =="\\") {
        return false;
    } else {
        return true;
    }
}
</script>
<!-- Check special characters in username end -->

<!-- in your form -->
    User id : <input type="text" id="txtname" name="txtname" onkeypress="return check(event)"/>

Answer 12

just the numbers:

$('input.time').keydown(function(e) { if(e.keyCode>=48 && e.keyCode<=57) { return true; } else { return false; } });

or for time including ":"

$('input.time').keydown(function(e) { if(e.keyCode>=48 && e.keyCode<=58) { return true; } else { return false; } });

also including delete and backspace:

$('input.time').keydown(function(e) { if((e.keyCode>=46 && e.keyCode<=58) || e.keyCode==8) { return true; } else { return false; } });

unfortuneatly not getting it to work on a iMAC

Answer 13

Wanted to comment on Alex's comment to Dale's answer. Not possible (first need how much "rep"? That wont happen very soon.. strange system.) So as an answer:

Backspace can be added by adding \b to the regex definition like this: [a-zA-Z0-9\b]. Or you simply allow the whole Latin range, including more or less anything "non exotic" characters (also control chars like backspace): ^[\u0000-\u024F\u20AC]+$

Only real unicode char outside latin there is the euro sign (20ac), add whatever you may need else.

To also handle input entered via copy&paste, simply also bind to the "change" event and check the input there too - deleting it or striping it / giving an error message like "not supported characters"..

if (!regex.test($j(this).val())) {
  alert('your input contained not supported characters');
  $j(this).val('');
  return false;
}

Answer 14

Restrict specials characters on keypress. Here's a test page for key codes: http://www.asquare.net/javascript/tests/KeyCode.html

var specialChars = [62,33,36,64,35,37,94,38,42,40,41];

some_element.bind("keypress", function(event) {
// prevent if in array
   if($.inArray(event.which,specialChars) != -1) {
       event.preventDefault();
   }
});

In Angular, I needed a proper currency format in my textfield. My solution:

var angularApp = angular.module('Application', []);

...

// new angular directive
angularApp.directive('onlyNum', function() {
    return function( scope, element, attrs) {

        var specialChars = [62,33,36,64,35,37,94,38,42,40,41];

        // prevent these special characters
        element.bind("keypress", function(event) {
            if($.inArray(event.which,specialChars) != -1) {
                prevent( scope, event, attrs)
             }
        });

        var allowableKeys = [8,9,37,39,46,48,49,50,51,52,53,54,55,56
            ,57,96,97,98,99,100,101,102,103,104,105,110,190];

        element.bind("keydown", function(event) {
            if($.inArray(event.which,allowableKeys) == -1) {
                prevent( scope, event, attrs)
            }
        });
    };
})

// scope.$apply makes angular aware of your changes
function prevent( scope, event, attrs) {
    scope.$apply(function(){
        scope.$eval(attrs.onlyNum);
        event.preventDefault();
    });
    event.preventDefault();
}

In the html add the directive

<input only-num type="text" maxlength="10" id="amount" placeholder="$XXXX.XX"
   autocomplete="off" ng-model="vm.amount" ng-change="vm.updateRequest()">

and in the corresponding angular controller I only allow there to be only 1 period, convert text to number and add number rounding on 'blur'

...

this.updateRequest = function() {
    amount = $scope.amount;
    if (amount != undefined) {
        document.getElementById('spcf').onkeypress = function (e) {
        // only allow one period in currency
        if (e.keyCode === 46 && this.value.split('.').length === 2) {
            return false;
        }
    }
    // Remove "." When Last Character and round the number on blur
    $("#amount").on("blur", function() {
      if (this.value.charAt(this.value.length-1) == ".") {
          this.value.replace(".","");
          $("#amount").val(this.value);
      }
      var num = parseFloat(this.value);
      // check for 'NaN' if its safe continue
      if (!isNaN(num)) {
        var num = (Math.round(parseFloat(this.value) * 100) / 100).toFixed(2);
        $("#amount").val(num);
      }
    });
    this.data.amountRequested = Math.round(parseFloat(amount) * 100) / 100;
}

...

Answer 15

To replace special characters, space and convert to lower case

$(document).ready(function (){
  $(document).on("keyup", "#Id", function () {
  $("#Id").val($("#Id").val().replace(/[^a-z0-9\s]/gi, '').replace(/[_\s]/g, '').toLowerCase());
 }); 
});

Answer 16

[User below code to restrict special character also    

$(h.txtAmount).keydown(function (event) {
        if (event.shiftKey) {
            event.preventDefault();
        }
        if (event.keyCode == 46 || event.keyCode == 8) {
        }
        else {
            if (event.keyCode < 95) {
                if (event.keyCode < 48 || event.keyCode > 57) {
                    event.preventDefault();
                }
            }
            else {
                if (event.keyCode < 96 || event.keyCode > 105) {
                    event.preventDefault();
                }
            }
        }


    });]

Answer 17

$(function(){
      $('input').keyup(function(){
        var input_val = $(this).val();
        var inputRGEX = /^[a-zA-Z0-9]*$/;
        var inputResult = inputRGEX.test(input_val);
          if(!(inputResult))
          {     
            this.value = this.value.replace(/[^a-z0-9\s]/gi, '');
          }
       });
    });