Develop Reference

Restricting users from inserting spaces, capitol letters, first value as int in textbox using jquery

I have a form in which I want users to only put alphabets, numbers
I want to restrict them from
Using the number as first value Eg. 1abc
Using Capitol letters Eg. 1ABc
Using Spaces Eg. 1 ab CD d5
I only want like abc1 OR a1bc OR f25fhgfh45w
I tried http://jsfiddle.net/m7QrG/506/ but it didn't help me out.

You can use RegExp /^\d|[A-Z\s]+/g to match digit at beginning of string or uppercase letters or space, remove i flag and $ anchor, use input event to also handle user pasting at <input> element
$('.alphaonly').on('input', function() {
$(this).val(function(i, val) {
return val.replace(/^\d|[A-Z\s]+/g, '');
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input name="lorem" class="alphaonly">

After observing your question and your comments with #guest271314 I came up to with the solution:
$(function() {
var haveFirst = false;
$('.alphaonly').on('keypress', function (event) {
if( $(this).val().length === 0 ) {
haveFirst = false;
}
var regex = new RegExp("^[a-z0-9_]+$");
var first = new RegExp("^[a-z]+$");
var key = String.fromCharCode(!event.charCode ? event.which : event.charCode);
if(!first.test(key) && haveFirst == false){
event.preventDefault();
return false;
}else if(regex.test(key)){
haveFirst = true;
}
if (!regex.test(key)) {
event.preventDefault();
return false;
}
});
})
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input name="lorem" class="alphaonly">
In hoping it will work as you want!

jQuery method that disallows input of certain chars

I'm trying to make a jQuery method that would delete wanted chars from selected elements.
For example:
$("input").disallowChars(/\D/g);// should disallow input of all non-digit elements in input elements
This is how I thought to do it, but it doesn't seem to work:
$.fn.disallowChars = function(regexp){
this.keyup(function(){
var value = $(this).val();
value.replace(regexp, "");
$(this).val(value);
});
return this;
};
$("input").disallowChars(/\D/g);
I'm a total newbie at this, how can I make it work.
Thanks

You could use String.fromCharCode() and keypress event instead:
$.fn.disallowChars = function(regexp){
return this.keypress(function(e){
if(String.fromCharCode(e.which).match(regexp)) return false;
});
};
DEMO
BUT doesn't disable any characters to be paste in input using mouse or paste keyboard shortcut.
On modern browsers, you could use input event, or change keyup paste mouseup (ya mouseup, to handle dropped text too):
$.fn.disallowChars = function(regexp){
return this.on('input', function(){
this.value = this.value.replace(regexp, '');
});
};
BUT then once input value is replaced, text carret is put in end (or start depending browser behaviour) of string input.
DEMO

heres a handy routine I use to sanitize some input fields in a current project:
// REPLACE SELECTOR WITH YOUR ID(S) OR SELECTORS...
$('input').bind("change keyup", function() {
var val = $.trim($(this).val());
// READ UP ON REGEX TO UNDERSTAND WHATS GOING ON HERE... ADD CHARACTERS YOU WANT TO ELIMINATE...
var regex = /[":'/\+;<>&\\/\n]/g;
if (val.match(regex)) {
val = val.replace(regex, "");
$(this).val($.trim(val));
}
});
Heres another version I used recently:
$("#myField").on("keypress", function(event) {
// THIS ONLY ALLOWS A-Z, A-Z, 0-9 AND THE # SYMBOL... just change stuffToAllow to suit your needs
var stuffToAllow = /[A-Za-z0-9# ]/g;
var key = String.fromCharCode(event.which);
if (event.keyCode == 8 || event.keyCode == 37 || event.keyCode == 39 || stuffToAllow.test(key)) {
return true;
}
alert( key + ' character not allowed!');
return false;
});

Remove only second character in jQuery

$('input').keypress(function(e){
if(($(this).val().split('a').length - 1) > 0){
console.log($('input').val());
$('input').val($('input').val().replace('a', ''));
}
})
jsfiddle: http://jsfiddle.net/Ht8rU/
I want have only one "a" in input. I check if length a > 1 and next remove "a" from input, but this not working good. I would like remove only second a from this input. One "a" is allow.

Edit: Oh I see now... If you want to keep only the first a you can try this:
$('input').keypress(function(e) {
var key = String.fromCharCode(e.which);
if (/a/i.test(key) && /a+/i.test(this.value)) {
e.preventDefault();
}
});
Demo: http://jsfiddle.net/elclanrs/Ht8rU/6/
You have to check if the current letter being typed is a:
if (String.fromCharCode(e.which) == 'a')
But here's a simplified version. You don't need to use val() if you can use value, specially because it makes your code cleaner. Also you might want to check for A or a so a regex might be a better option. Here's the code:
$('input').keypress(function(e) {
var A = /a/gi,
letter = String.fromCharCode(e.which);
if (A.test(letter)) {
$(this).val(this.value.replace(A,''));
}
});
Demo: http://jsfiddle.net/elclanrs/Ht8rU/3/

I suggest using preventDefault to stop the key from being pressed:
$('input').keypress(function(e) {
if (e.keyCode === 97 && $(this).val().split('a').length > 1) {
e.preventDefault();
}
});
JSFiddle

This code may seem long and without any usefulness, but it works.
$('input').keyup(function(e) {
var e = $(this),
val = e.val(),
aPos = val.indexOf('a'),
spl1 = val.substring(0, aPos + 1),
spl2 = val.substring(aPos, val.length).replace(/a/gi, ''),
v = spl1 + spl2;
e.val(v);
});
Here is a working JSFiddle of this.

I would try something like this. Not sure how well supported is the input event currently, though.
(function() {
var elem = $('input');
var value = elem.val();
elem.bind("input propertychange", function(e) {
if (elem.val().split('a').length - 1 > 1)
elem.val(value);
else
value = elem.val();
});
})();
http://jsfiddle.net/Ht8rU/8/

When the user presses 'a' or 'A', you can check if there is one 'a' or 'A' already present, if there is one already then you don't add it to the input.
$('input').keypress(function(e){
if ((e.keyCode === 65 || e.keyCode === 97) & $(this).val().match(/a/gi) !== null) e.preventDefault();
})
Updated jsFiddle

Here's a modified version of your fiddle that works: http://jsfiddle.net/orlenko/zmebS/2/
$('input').keypress(function(e){
var that = $(this);
var parts = that.val().split('a');
if (parts.length > 2) {
parts.splice(1, 0, 'a');
that.val(parts.join(''));
} else {
// no need to replace
}
})
Note that we only replace the contents of the input if we have to - otherwise, constant rewriting of the contents will make it impossible to type in the midle or at the beginning of the text.
If you want to further improve it and make it possible to type at the beginning even when we are replacing the contents, check out this question about detecting and restoring selection: How to get selected text/caret position of an input that doesn't have focus?

How to restrict single word (that itselft having only string not number) while entering value in inputbox

Im using this code to restrict the user to not enter special characters
$("input").keyup(function(){
var text=$(this).val();
$(this).val(text.replace(/[^\w\d\s]/,""));
})
I want to restrict the user to enter only one word without space and also having no numbers and special characters. like this
myword #valid
myword2 #invalid
myword secondword #invalid

$(this).val(text.replace(/[^A-Za-z]/g,''));
Test it here »

here's a jQuery plugin that will prevent typing keys that are not in the specified regex. It also works if you paste something, but that works with replace.
$("body").delegate("[keyfilter]", "keypress", function(event) {
var elem = $(this), filter = elem.attr('keyfilter');
if (event.charCode === 0) {
return;
}
try {
if (!String.fromCharCode(event.charCode).match(new RegExp("[" + filter + "]"))) {
event.preventDefault();
event.stopImmediatePropagation();
}
} catch(e) {}
}).delegate("[keyfilter]", "paste", function(event) {
var elem = $(this), filter = elem.attr('keyfilter');
setTimeout(function() { elem.val(elem.val().match(new RegExp("[" + filter + "]"))[0]) }, 50);
});
the way to use it:
<input type="text" keyfilter="A-Za-z" />

Javascript Regex Only Textbox

I was able to find the solution for this in c# / .net but not for regular web html. If there's already an answer let me know and i'll close question.
How to create a text box that only will allow certain characters (ex. alphanumeric) based on a given regex (ex. [a-zA-Z0-9])? So if a user tries to enter anything else, paste included, it is removed or not allowed.
<input type="text" class="alphanumericOnly">

The basic function would be this:
string = string.replace(/[^a-zA-Z0-9]/g, '')
This would replace any character that is not described by [a-zA-Z0-9].
Now you could either put it directly into your element declaration:
<input type="text" class="alphanumericOnly" onkeyup="this.value=this.value.replace(/[^a-zA-Z0-9]/g, '')">
Or (as you used the class hint) you assign this behavior to every input element with the class alphanumericOnly:
var inputElems = document.getElemenstByTagName("input");
for (var i=0; i<inputElems.length; i++) {
var elem = inputElems[i];
if (elem.nodeName == "INPUT" && /(?:^|\s+)alphanumericOnly(?:\s+|$)/.test(elem.className) {
elem.onkeyup = function() {
this.value = this.value.replace(/[^a-zA-Z0-9]/g, '');
}
}
}
But it’s probably easier to do that with jQuery or another JavaScript framework:
$("input.alphanumericOnly").bind("keyup", function(e) {
this.value = this.value.replace(/[^a-zA-Z0-9]/g, '');
});

Example on how to allow alphanumeric chars and space (a-z, A-Z, 0-9 and space, others are eliminated as typed):
$('#some_input_field_id').unbind('change keyup paste mouseup').bind('change keyup paste mouseup', function(){if(this.value.match(/[^a-zA-Z0-9 ]/g)){this.value = this.value.replace(/[^a-zA-Z0-9 ]/g, '');}});
Eample on how to allow only lowercase alpha chars (a-z, others are eliminated as typed):
$('#some_input_field_id').unbind('change keyup paste mouseup').bind('change keyup paste mouseup', function(){if(this.value.match(/[^a-z]/g)){this.value = this.value.replace(/[^a-z]/g, '');}});
etc...

Assuming you have the input stored as the variable input...
input.onkeyup(function(e) {
this.value = this.value.replace(/\W/g, '');
}
After every keypress the value of the input will be stripped of any non-alphanumeric characters.

If you use a .replace method on the keyup event the input will flicker with the non-alphanumeric characters as they're typed, which appears sloppy and doesn't comply with OCD folks like myself.
A cleaner approach would be to bind to the keypress event and deny the characters before they even arrive at the input, like the following:
$('.alphanumericOnly').keypress(function(e){
var key = e.which;
return ((key >= 48 && key <= 57) || (key >= 65 && key <= 90) || (key >= 95 && key <= 122));
});
A list of basic keycodes can be found here if this particular set doesn't suit your specific needs.

I've noticed that at least in my case, with the paste and drop events, replacing the text wasn't working because at that point the value property of the input was still the previous one. So I did this:
With pure javascript:
function filterInputs() {
var that = this;
setTimeout(function() {
that.value = that.value.replace(/[^a-zA-Z0-9]/g, '');
}, 0);
}
var input = document.getElementById('theInput');
input.addEventListener('keyup', filterInputs);
input.addEventListener('paste', filterInputs);
input.addEventListener('drop', filterInputs);
input.addEventListener('change', filterInputs);
Try writing non-alphanumeric characters: <input type="text" id="theInput">
<br>You can use this input to write anything and copy-paste/drag & drop it into the other one: <input type="text">
With jQuery:
function filterInputs() {
var that = this;
setTimeout(function() {
that.value = that.value.replace(/[^a-zA-Z0-9]/g, '');
}, 0);
}
$('#theInput').on('keyup paste drop change', filterInputs);
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
Try writing non-alphanumeric characters: <input type="text" id="theInput">
<br>You can use this input to write anything and copy-paste/drag & drop it into the other one: <input type="text">