I'm trying to validate a character to make sure it's a letter (not a number, symbol, etc.) BEFORE it's allowed to be entered into the form field. How can I do that with JavaScript?
Here is something I tried:
<script type="text/javascript">
function checkTest() {
var letterValue = document.forms[0].test.value;
var letterCheck = /[a-z]/i;
var letterTest = letterValue.test(letterCheck);
}
</script>
<html>
<body>
<form>
<input type="text" name="test" onkeypress="checkTest();"/>
</form>
</body>
</html>
This code will check the string of the value. I've tried using var letterLeng= letterValue.length and then using var letterChar = letterValue.charAt(letterLeng) or even var letterChar = letterValue.charAt(letterLeng - 1) and all to no avail. Any advice would be much appreciated.
Ask the event for the key that was pressed then test it:
function checkTest(event) {
event = event || window.event;
if (!/[A-Za-z]/.test(String.fromCharCode(event.keyCode || event.which))) {
if (event.preventDefault)
event.preventDefault();
else
event.returnValue = false;
}
}
<input type="text" name="test" onkeypress="checkTest(event);"/>
I like Alex K's answer, but I could not get the 'onkeypress' handler to work so I tried something using Jquery. It doesn't keep the bad letters from appearing briefly, but it does keep them from being entered.
It uses the 'keyup' event, which actually makes checking for the key code much easier in this instance since you want to limit it to [a-zA-Z]
$("#myinput").on("keyup", function (e) {
// Ignore the shift key.
if (e.keyCode === 16) {
return true;
}
if ((e.keyCode < 65 || e.keyCode > 90)) {
var str = $("#myinput").val();
$("#myinput").val(str.slice(0, str.length - 1));
}
});
The working fiddle is here: http://jsfiddle.net/yaa9snce/
What you are looking for is the onkeypress event.
<input type="text" onkeypress="myFunction()">
<script>
function myFunction() {
alert("You pressed a key inside the input field");
}
</script>
Related
Hello I'm trying to make real time input type="text" filter which allows only numbers and dot, using javascript.
I wrote
Javascript:
<script>
function thirdTaskFunction(evnt) {
evnt = evnt || window.event;
var charCode = evnt.which ? evnt.which : evnt.keyCode;
return /\d/.test(String.fromCharCode(charCode));
}
function thirdTaskFunction(evt) {
var charCode = (evt.which) ? evt.which : evt.keyCode;
if(charCode > 31 && (charCode < 48 || charCode > 57)) {
return false;
}
return true;
}
function thirdTaskFunction() {
var thirdInput = document.getElementById("thirdTaskInputText");
thirdInput = thirdInput.onchange = thirdTaskFuncion;
var valid = /^\-?\d+\.\d*$|^\-?[\d]*$/;
var number = /\-\d+\.\d*|\-[\d]*|[\d]+\.[\d]*|[\d]+/;
if(!valid.test(this.value)) {
var compare = this.value.match(number);
this.value = compare ? compare[0] : '';
}
}
</script>
HTML:
<div id="thirdTaskDIV">
<input id="thirdTaskInputText" type="text" placeholder="Type a number" autofocus onkeypressed="return thirdTaskFunction(event);">
</div>
I was trying many ways, every thirdTaskFunction() method wasn't work, I was tested solution on w3schools so maybe this is reason? But I think that I dont remember about something that make it works. And I know is very similar to "HTML text input allow only numeric input" but it didnt works.. So I hope somebody show me whats pappyn here.
One way to allow only numbers in an input field is using a keypress event listener. So you'll want to select the input field and give it an event listener, like this:
const inputField = document.querySelector("/*input field id here*/");
inputField.addEventListener("keypress", function(e){
if(e.keyCode > 48 && e.keyCode < 57){
e.preventDefault();
}
}
This function checks if the key that's pressed matches a number key, and if it doesn't, prevents the default action which in this case is printing the character to the input field.
If you have any questions, I'll do my best to answer them!
P.S. The keyCode numbers used are estimates based on memory, to get the key codes simply do a quick search on google for "ASCII key codes".
The event code (NOT keyCode since the keyCode property is deprecated) for the dot is Period and the event code for the numbers 0 to 9 comes in the form Digit0, Digit1 and so on.
Just use the keydown event listener to retrieve the event code and then use the includes() method to check if the current key has a code that includes "Digit" or "Period" and restrict input of that character if it doesn't include either of those two by using preventDefault() like this:
const input = document.getElementById('thirdTaskInputText');
function checkKey(e) {
if(e.code.includes("Digit") || e.code.includes("Period")) {
console.log("valid input");
} else {
e.preventDefault();
console.log("not a number!");
}
}
input.addEventListener('keydown', checkKey)
<input id="thirdTaskInputText" type="text" placeholder="Type a number">
Without the console logs, you can further simplify the above code to a single if statement using the bang operator ! like this:
const input = document.getElementById('thirdTaskInputText');
function checkKey(e) {
if(!(e.code.includes("Digit") || e.code.includes("Period"))) e.preventDefault();
}
input.addEventListener('keydown', checkKey)
<input id="thirdTaskInputText" type="text" placeholder="Type a number">
I've seen a similar question on SO but my approach is slightly different. I have a textarea that I want to accept only numbers as an input. Currently all inputs are allowed and the error alert isn't triggered.
I think the problem may be that the key being pressed isn't being passed into my validate function, but I'm not sure how to do that without using the html onkeypress which I'm trying to avoid using.
HTML:
<textarea id="noteNumberInput" placeholder="Note number"></textarea>
JS:
$(document).ready(function () {
var noteNumberInput = document.getElementById("noteNumberInput");
//VALIDATE NOTE NUMBER TEXTAREA
function validate() {
var keycode = (key.which) ? key.which : key.keyCode;
//comparing pressed keycodes
if (keycode < 48 || keycode > 57) {
alert("Please only enter the note number e.g. '1', '2' etc.")
return false;
}
}
noteNumberInput.addEventListener("keypress", validate);
});
Your function needs the key parameter:
function validate(key) {
....
Is there a way to block users from writing specific characters in input fields? I tried the code below, but when a user enters disallowed characters, they appear for a brief period before disappearing. I want the input to remain unchanged when invalid characters are written.
I want to use onchange because other restriction methods do not seem to work on mobile devices. The problem I want to solve is that characters appear briefly before being removed.
function checkInput(ob) {
const invalidChars = /[^0-9]/gi;
if(invalidChars.test(ob.value)) {
ob.value = ob.value.replace(invalidChars, "");
}
};
<input class="input" maxlength="1" onChange="checkInput(this)" onKeyup="checkInput(this)" type="text" autocomplete="off" />
you can use try this,
$('.input').keyup(function () {
if (!this.value.match(/[0-9]/)) {
this.value = this.value.replace(/[^0-9]/g, '');
}
});
SEE THIS FIDDLE DEMO
Updated :
You can try this Code,
$(document).ready(function() {
$(".input").keydown(function (e) {
// Allow: backspace, delete, tab, escape and enter
if ($.inArray(e.keyCode, [46, 8, 9, 27, 13, 110]) !== -1 ||
// Allow: Ctrl+A
(e.keyCode == 65 && e.ctrlKey === true) ||
// Allow: home, end, left, right
(e.keyCode >= 35 && e.keyCode <= 39)) {
// let it happen, don't do anything
return;
}
// Ensure that it is a number and stop the keypress
if ((e.shiftKey || (e.keyCode < 48 || e.keyCode > 57)) && (e.keyCode < 96 || e.keyCode > 105)) {
e.preventDefault();
}
});
});
SOURCE
SEE UPDATED FIDDLE DEMO
UPDATED FOR ANDROID:
<EditText
android:id="#+id/editText1"
android:inputType="number"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/textView1"
android:layout_marginTop="58dp"
android:layout_toRightOf="#+id/textView1"
android:maxLength="1" >
</EditText>
I think it may help you... using android:inputType="number" you can do that.
A combination of keypress and paste events does a trick:
var text = document.getElementById('text');
text.onkeypress = text.onpaste = checkInput;
function checkInput(e) {
var e = e || event;
var char = e.type == 'keypress'
? String.fromCharCode(e.keyCode || e.which)
: (e.clipboardData || window.clipboardData).getData('Text');
if (/[^\d]/gi.test(char)) {
return false;
}
}
<input class="input" maxlength="10" id="text" type="text" autocomplete="off" />
This code prevents from typing or pasting anything but a number. Also no blinking and invalid characters don't show up.
Works in IE7+.
Demo: http://jsfiddle.net/VgtTc/3/
All answers given so far suffer from at least one of the following accessibility issues:
They validate key codes, which does not work with non-QWERTY keyboard layouts.
They do not cover all input methods; especially drag&drop is often forgotten.
They alter the value, which resets the position of the caret.
They use the pattern attribute, but this does not provide feedback until the form is submitted.
Wouldn't it be a much better idea to actually validate the input before it's inserted?
The beforeinput event fires before the input's value is changed. The event has a data property which describes the content that the user wants to add to the input field. In the event handler, you simply check the data attribute, and stop the event chain if it contains disallowed characters.
We end up with the following very simple, very short code.
const input = document.getElementById("input");
const regex = new RegExp("^[0-9]*$");
input.addEventListener("beforeinput", (event) => {
if (event.data != null && !regex.test(event.data))
event.preventDefault();
});
<label for="input">Enter some digits:</label>
<input id="input" />
Some closing notes:
Accessibility: Provide a clear explanation of what input format is expected from the user. For example, you can use the title attribute of the input to show a tooltip explaining the expected format.
Security: This is client-side validation, and does not guarantee that the pattern is enforced when the form is sent to a server. For that, you'll need server-side validation.
Here's a little hack you could try: DEMO
What it does is that it colors every input text white and then changes it back to black if it suits your requirements. If you could live with the bit of lag that occurs when you enter a valid character.
function checkInput(ob) {
var invalidChars = /[^0-9]/gi
if (invalidChars.test(ob.value)) {
ob.value = ob.value.replace(invalidChars, "");
}
else {
document.getElementById('yourinput').style.color = '#000';
}
};
function hideInput(ob) {
document.getElementById('yourinput').style.color = '#FFF';
};
html
<input id="yourinput" class="input" maxlength="1" onKeydown="hideInput(this)" onKeyup="checkInput(this)" type="text" autocomplete="off" />
css
input {color:#FFF;}
check this code,
$('.input').keypress(function(e) {
var a = [];
var k = e.which;
for (i = 48; i < 58; i++)
a.push(i);
if (!(a.indexOf(k)>=0))
e.preventDefault();
});
<input id="testInput"></input>
<script>
testInput.onchange = testInput.oninput = restrict;
function restrict() {
testInput.value = testInput.value.replace(/[^a-z]/g, "");
}
</script>
I came up with something slightly different. oninput instead of onkeyup/onkeydown, and onchange instead of onpaste.
I restrict invalid characters on both keypress and paste events like:
<input type="text" onkeydown="validateKey(event)" onpaste="validatePaste(this, event)">
And define functions to handle these events inside tab or a separate javascript file:
<script>
function validateKey(e) {
switch(e.keyCode) {
case 8,9,13,37,39:
break;
default:
var regex = /[a-z .'-]/gi;
var key = e.key;
if(!regex.test(key)) {
e.preventDefault();
return false;
}
break;
}
}
function validatePaste(el, e) {
var regex = /^[a-z .'-]+$/gi;
var key = e.clipboardData.getData('text')
if (!regex.test(key)) {
e.preventDefault();
return false;
}
}
</script>
I know this is a really simple question, but how do I add content to a div when the user types into a input field and hits enter?
I have tried:
document.addEventListener('keydown', function(e){
if(e.keyCode === 13) {
function bleh() {
var from = document.getElementById('setter').value;
x = document.getElementById("mything");
x.innerHTML = from;
}
}
})
my HTML is:
<input type="text" autofocus="autofocus" id="setter"
onkeydown="writeit(this, event);moveIt(this.value.length, event)"
onkeyup="writeit(this, event)" onkeypress="writeit(this, event);"></input>
if you want to see it in action, go to thomaswd.com/cmd. start typing and hit enter.
again, this sounds like a really simple question, but I cant get it working. Thanks!!!
You were really close:
document.getElementById("setter").addEventListener('keydown', function(e){
if(e.keyCode === 13) {
var from = this.value;
x = document.getElementById("mything");
x.innerHTML = from;
}
})
JSFiddle: http://jsfiddle.net/9bbR2/
Although I would recommend using jQuery, it's much simpler.
$(function() {
$("#setter").keydown(function(e) {
if(e.keyCode === 13) {
$("#mything").text($(this).val());
}
});
});
I would like to have an input that would change to upper case on keyup. So I attach a simple event on keyup.
HTML
<input id="test"/>
Javascript (with jQuery)
$("#test").keyup(function(){
this.value = this.value.toUpperCase();
});
But I found that in Chrome and IE, when you push left arrow, the cursor automatically move to end. I notice that I should detect if the input is letter only. Should I use keycode range or regexp for detection?
Example: http://jsbin.com/omope3
Or you can use the following (this is probably faster and more elegant):
<input style="text-transform: uppercase" type='text'></input>
But that sends the as-typed value back in the form data, so use either of the following to store it as all-caps in the database:
MySQL: UPPER(str)
PHP: strtoupper()
Another solution, if you use the text-transform: uppercase; css property:
<input id='test' style='text-transform: uppercase;' type='text'></input>
And with jQuery help you choose the blur event:
$("#test").blur(function(){
this.value = this.value.toUpperCase();
});
With this solution, you don't have to upper the database fields, you can use the cursor for movement and the user can insert/rewrite the text in the input field.
Use this:
<input onkeyup="MakeMeUpper(this)" type="text"/>
And in your JS Code Part put:
function MakeMeUpper(f, e){
var actualValue = f.value;
var upperValue = f.value.toUpperCase();
if( actValue != upperValue){
f.value = upperValue;
}
}
This code won't change the text if the user entered something that is not text (left or right arrow).
Yeah, looks like some browsers move the cursor to the end when the value gets updated. You could do this:
$("#test").keyup(function(){
var upper = this.value.toUpperCase();
if (this.value != upper)
this.value = upper;
});
which will only change the value if it needs to be changed. However, that still leaves you with the problem that if you type abd, move left, hit c to get abcd, the cursor will still get moved to the end.
Javascript (with jQuery)
$("#test").keyup(function(){
$(this).val($(this).val().toUpperCase());
});
var str = $(this).val();
if (evt.keyCode != 37 && evt.keyCode != 39)
{
str = str.toLowerCase().replace(/\b[a-z]/g, function(letter) {
return letter.toUpperCase();
});
$(this).val(str);
}
You probably want to look at keyCode in your keyup function.
var UP_ARROW = 38,
DOWN_ARROW = 40;
$('#test').keyup(function(evt){
if (evt.keyCode == UP_ARROW)
{
this.value = this.value.toUpperCase();
}
if (evt.keyCode == DOWN_ARROW)
{
this.value = this.value.toLowerCase();
}
});