jquery - validate characters on keypress?

Question

I have a form text field that I want to allow only numbers and letters in. (i.e., no #$!, etc...) Is there a way to throw up an error and prevent the keypress from actuall

Answer 1

I found that combining validation on keypress and keyup gives the best results. Key up is a must if you want to handle copy pasted text. It is also a catch all in case of cross browser issues which allow non numeric values into your textbox.

    $("#ZipCode").keypress(function (event) {

        var key = event.which || event.keyCode; //use event.which if it's truthy, and default to keyCode otherwise

        // Allow: backspace, delete, tab, and enter
        var controlKeys = [8, 9, 13];
        //for mozilla these are arrow keys
        if ($.browser.mozilla) controlKeys = controlKeys.concat([37, 38, 39, 40]);

        // Ctrl+ anything or one of the conttrolKeys is valid
        var isControlKey = event.ctrlKey || controlKeys.join(",").match(new RegExp(key));

        if (isControlKey) {return;}

        // stop current key press if it's not a number
        if (!(48 <= key && key <= 57)) {
            event.preventDefault();
            return;
        }
    });

$('#ZipCode').keyup(function () {
    //to allow decimals,use/[^0-9\.]/g 
    var regex = new RegExp(/[^0-9]/g);
    var containsNonNumeric = this.value.match(regex);
    if (containsNonNumeric)
        this.value = this.value.replace(regex, '');
});

Answer 2

Well the patrick's answer removes character if it is wrong, to actually prevent character from being inserted into the field use

$("#field").keypress(function(e) {
    // Check if the value of the input is valid
    if (!valid)
        e.preventDefault();
});

This way the letter will not come to textarea

Answer 3

$('input').keyup(function() {
    var $th = $(this);
    $th.val( $th.val().replace(/[^a-zA-Z0-9]/g, function(str) { alert('You typed " ' + str + ' ".\n\nPlease use only letters and numbers.'); return ''; } ) );
});

---

EDIT:

There are some other good answers here that will prevent the input from taking place.

I've updated mine since you also wanted to show an error. The replace can take a function instead of a string. The function runs and returns a replacement value. I've added an alert to show the error.

http://jsfiddle.net/ntywf/2/

Answer 4

$(document).ready(function() {
 $('.ipFilter').keydown((e) => {
    if ($.inArray(e.keyCode, [46, 8, 9, 27, 13, 110, 190]) !== -1 ||
        (e.keyCode === 65 && (e.ctrlKey === true || e.metaKey === true) || 
          e.keyCode === 67 && (e.ctrlKey === true || e.metaKey === true) ||
          e.keyCode === 86 && (e.ctrlKey === true || e.metaKey === true) ||
          e.keyCode === 82 && (e.ctrlKey === true || e.metaKey === true)) || 
        (e.keyCode >= 35 && e.keyCode <= 40 )) {
             return;
    }
    if ((e.shiftKey || (e.keyCode < 48 || e.keyCode > 57)) && (e.keyCode < 96 || e.keyCode > 105)) {
        e.preventDefault();
    }
  });
});

Answer 5

$('#yourfield').keydown(function(e) {
    // Check e.keyCode and return false if you want to block the entered character.
});

Answer 6

The above jquery extension (ForceAlphaNumericOnly) is good but still allows the following characters through !@#$%^&*()

On my Mac, when you press the shift key (keycode 16) and then 1, it enters ! but the keycode is 49, the keycode for 1.