Develop Reference

No space at start of input does not work with a addEventListener

I been trying to figure out why this does not work with a event listener. This script prevents white space in the beginning of a input so I need to avoid using
this oninput="validate(this)" and convert this script into using a event listener instead I been trying to figure this out for a while now but no luck here is my code.
function validate(input){
if(/^\s/.test(input.value))
input.value = '';
}
<input id='noWhiteSpaceAtTheStart' oninput="validate(this)" type='text'/>

You can use input event or even keyup event. It fires everytime the input's text changes. As far as I know, input is supported in IE9+ and other modern browsers, and keyup is supported in all browsers.
Example with input event:
var input = document.getElementById("noWhiteSpaceAtTheStart");
input.addEventListener('input', function() {
if(/^\s/.test(input.value)) {
input.value = '';
}
});
Example with keyup event, this is a little uglier than the latter solution because the user can see the space being inputted and removed:
var input = document.getElementById("test");
input.addEventListener('keyup', function() {
if(/^\s/.test(input.value))
input.value = '';
});
Inputs that are changed with JavaScript must be triggered manually, and this can be done easily with jQuery by the following(may not work on native JavaScript events, have not tested):
var input = $("#input");
input.val("I am going through changes mom");
input.trigger("change");
Although, using pure JavaScript to do this is a little more complicated. Here is a link to help with that if needed
Here is a working codepen for you.

Above code works perfectly fine for me. Can you please attach a breakpoint to check is there something going wrong while the function is called.
Few better ways to implement this:
You can use
javascript addEventListner on this input text to ensure your code works
Use function like onKeyUp

Try this:
HTML:
<input id='noWhiteSpaceAtTheStart' type='text'/>
Javascript:
function validate(){
var val = event.target.value;
if(/^\s/.test(val))
event.target.value = '';
}
document.getElementById("noWhiteSpaceAtTheStart").addEventListener("input", validate);
Tested on chrome, it works.

How to call a function when default browser autocomplete list item selected [duplicate]

I have a pretty simple form. When the user types in an input field, I want to update what they've typed somewhere else on the page. This all works fine. I've bound the update to the keyup, change and click events.
The only problem is if you select an input from the browser's autocomplete box, it does not update. Is there any event that triggers when you select from autocomplete (it's apparently neither change nor click). Note that if you select from the autocomplete box and the blur the input field, the update will be triggered. I would like for it to be triggered as soon as the autocomplete .
See: http://jsfiddle.net/pYKKp/ (hopefully you have filled out a lot of forms in the past with an input named "email").
HTML:
<input name="email" />
<div id="whatever"><whatever></div>
CSS:
div {
float: right;
}
Script:
$("input").on('keyup change click', function () {
var v = $(this).val();
if (v) {
$("#whatever").text(v);
}
else {
$("#whatever").text('<whatever>');
}
});

I recommending using monitorEvents. It's a function provide by the javascript console in both web inspector and firebug that prints out all events that are generated by an element. Here's an example of how you'd use it:
monitorEvents($("input")[0]);
In your case, both Firefox and Opera generate an input event when the user selects an item from the autocomplete drop down. In IE7-8 a change event is produced after the user changes focus. The latest Chrome does generate a similar event.
A detailed browser compatibility chart can be found here:
https://developer.mozilla.org/en-US/docs/Web/Events/input

Here is an awesome solution.
$('html').bind('input', function() {
alert('test');
});
I tested with Chrome and Firefox and it will also work for other browsers.
I have tried a lot of events with many elements but only this is triggered when you select from autocomplete.
Hope it will save some one's time.

Add "blur". works in all browsers!
$("input").on('blur keyup change click', function () {

As Xavi explained, there's no a solution 100% cross-browser for that, so I created a trick on my own for that (5 steps to go on):
1. I need a couple of new arrays:
window.timeouts = new Array();
window.memo_values = new Array();
2. on focus on the input text I want to trigger (in your case "email", in my example "name") I set an Interval, for example using jQuery (not needed thought):
jQuery('#name').focus(function ()
{
var id = jQuery(this).attr('id');
window.timeouts[id] = setInterval('onChangeValue.call(document.getElementById("'+ id +'"), doSomething)', 500);
});
3. on blur I remove the interval: (always using jQuery not needed thought), and I verify if the value changed
jQuery('#name').blur(function ()
{
var id = jQuery(this).attr('id');
onChangeValue.call(document.getElementById(id), doSomething);
clearInterval(window.timeouts[id]);
delete window.timeouts[id];
});
4. Now, the main function which check changes is the following
function onChangeValue(callback)
{
if (window.memo_values[this.id] != this.value)
{
window.memo_values[this.id] = this.value;
if (callback instanceof Function)
{
callback.call(this);
}
else
{
eval( callback );
}
}
}
Important note: you can use "this" inside the above function, referring to your triggered input HTML element. An id must be specified in order to that function to work, and you can pass a function, or a function name or a string of command as a callback.
5. Finally you can do something when the input value is changed, even when a value is selected from a autocomplete dropdown list
function doSomething()
{
alert('got you! '+this.value);
}
Important note: again you use "this" inside the above function referring to the your triggered input HTML element.
WORKING FIDDLE!!!
I know it sounds complicated, but it isn't.
I prepared a working fiddle for you, the input to change is named "name" so if you ever entered your name in an online form you might have an autocomplete dropdown list of your browser to test.

Detecting autocomplete on form input with jQuery OR JAVASCRIPT
Using: Event input. To select (input or textarea) value suggestions
FOR EXAMPLE FOR JQUERY:
$(input).on('input', function() {
alert("Number selected ");
});
FOR EXAMPLE FOR JAVASCRIPT:
<input type="text" onInput="affiche(document.getElementById('something').text)" name="Somthing" />
This start ajax query ...

The only sure way is to use an interval.
Luca's answer is too complicated for me, so I created my own short version which hopefully will help someone (maybe even me from the future):
$input.on( 'focus', function(){
var intervalDuration = 1000, // ms
interval = setInterval( function(){
// do your tests here
// ..................
// when element loses focus, we stop checking:
if( ! $input.is( ':focus' ) ) clearInterval( interval );
}, intervalDuration );
} );
Tested on Chrome, Mozilla and even IE.

I've realised via monitorEvents that at least in Chrome the keyup event is fired before the autocomplete input event. On a normal keyboard input the sequence is keydown input keyup, so after the input.
What i did is then:
let myFun = ()=>{ ..do Something };
input.addEventListener('change', myFun );
//fallback in case change is not fired on autocomplete
let _k = null;
input.addEventListener( 'keydown', (e)=>_k=e.type );
input.addEventListener( 'keyup', (e)=>_k=e.type );
input.addEventListener( 'input', (e)=>{ if(_k === 'keyup') myFun();})
Needs to be checked with other browser, but that might be a way without intervals.

I don't think you need an event for this: this happens only once, and there is no good browser-wide support for this, as shown by #xavi 's answer.
Just add a function after loading the body that checks the fields once for any changes in the default value, or if it's just a matter of copying a certain value to another place, just copy it to make sure it is initialized properly.

How can I bind to the change event of a textarea in jQuery?

I want to capture if any changes happened to <textarea>. Like typing any characters (deleting,backspace) or mouse click and paste or cut. Is there a jQuery event that can trigger for all those events?
I tried change event, but it triggers the callback only after tabbing out from the component.
Use: I want to enable a button if a <textarea> contains any text.

Try this actually:
$('#textareaID').bind('input propertychange', function() {
$("#yourBtnID").hide();
if(this.value.length){
$("#yourBtnID").show();
}
});
DEMO
That works for any changes you make, typing, cutting, pasting.

bind is deprecated. Use on:
$("#textarea").on('change keyup paste', function() {
// your code here
});
Note: The code above will fire multiple times, once for each matching trigger-type. To handle that, do something like this:
var oldVal = "";
$("#textarea").on("change keyup paste", function() {
var currentVal = $(this).val();
if(currentVal == oldVal) {
return; //check to prevent multiple simultaneous triggers
}
oldVal = currentVal;
//action to be performed on textarea changed
alert("changed!");
});
jsFiddle Demo

Use an input event.
var button = $("#buttonId");
$("#textareaID").on('input',function(e){
if(e.target.value === ''){
// Textarea has no value
button.hide();
} else {
// Textarea has a value
button.show();
}
});

This question needed a more up-to-date answer, with sources. This is what actually works (though you don't have to take my word for it):
// Storing this jQuery object outside of the event callback
// prevents jQuery from having to search the DOM for it again
// every time an event is fired.
var $myButton = $("#buttonID")
// input :: for all modern browsers [1]
// selectionchange :: for IE9 [2]
// propertychange :: for <IE9 [3]
$('#textareaID').on('input selectionchange propertychange', function() {
// This is the correct way to enable/disabled a button in jQuery [4]
$myButton.prop('disabled', this.value.length === 0)
}
1: https://developer.mozilla.org/en-US/docs/Web/Events/input#Browser_compatibility
2: oninput in IE9 doesn't fire when we hit BACKSPACE / DEL / do CUT
3: https://msdn.microsoft.com/en-us/library/ms536956(v=vs.85).aspx
4: http://api.jquery.com/prop/#prop-propertyName-function
BUT, for a more global solution that you can use throughout your project, I recommend using the textchange jQuery plugin to gain a new, cross-browser compatible textchange event. It was developed by the same person who implemented the equivalent onChange event for Facebook's ReactJS, which they use for nearly their entire website. And I think it's safe to say, if it's a robust enough solution for Facebook, it's probably robust enough for you. :-)
UPDATE: If you happen to need features like drag and drop support in Internet Explorer, you may instead want to check out pandell's more recently updated fork of jquery-splendid-textchange.

2018, without JQUERY
The question is with JQuery, it's just FYI.
JS
let textareaID = document.getElementById('textareaID');
let yourBtnID = document.getElementById('yourBtnID');
textareaID.addEventListener('input', function() {
yourBtnID.style.display = 'none';
if (textareaID.value.length) {
yourBtnID.style.display = 'inline-block';
}
});
HTML
<textarea id="textareaID"></textarea>
<button id="yourBtnID" style="display: none;">click me</div>

Here's another (modern) but slightly different version than the ones mentioned before. Tested with IE9:
$('#textareaID').on('input change keyup', function () {
if (this.value.length) {
// textarea has content
} else {
// textarea is empty
}
});
For outdated browsers you might also add selectionchange and propertychange (as mentioned in other answers). But selectionchange didn't work for me in IE9. That's why I added keyup.

try this ...
$("#txtAreaID").bind("keyup", function(event, ui) {
// Write your code here
});

Try to do it with focusout
$("textarea").focusout(function() {
alert('textarea focusout');
});

.delegate is the only one that is working to me with jQuery JavaScript Library v2.1.1
$(document).delegate('#textareaID','change', function() {
console.log("change!");
});

After some experimentation I came up with this implementation:
$('.detect-change')
.on('change cut paste', function(e) {
console.log("Change detected.");
contentModified = true;
})
.keypress(function(e) {
if (e.which !== 0 && e.altKey == false && e.ctrlKey == false && e.metaKey == false) {
console.log("Change detected.");
contentModified = true;
}
});
Handles changes to any kind of input and select as well as textareas ignoring arrow keys and things like ctrl, cmd, function keys, etc.
Note: I've only tried this in FF since it's for a FF add-on.

Try this
$('textarea').trigger('change');
$("textarea").bind('cut paste', function(e) { });

Can jQuery check whether input content has changed?

Is it possible to bind javascript (jQuery is best) event to "change" form input value somehow?
I know about .change() method, but it does not trigger until you (the cursor) leave(s) the input field. I have also considered using .keyup() method but it reacts also on arrow keys and so on.
I need just trigger an action every time the text in the input changes, even if it's only one letter change.

There is a simple solution, which is the HTML5 input event. It's supported in current versions of all major browsers for <input type="text"> elements and there's a simple workaround for IE < 9. See the following answers for more details:
jQuery keyboard events
Catch only keypresses that change input?
Example (except IE < 9: see links above for workaround):
$("#your_id").on("input", function() {
alert("Change to " + this.value);
});

Yes, compare it to the value it was before it changed.
var previousValue = $("#elm").val();
$("#elm").keyup(function(e) {
var currentValue = $(this).val();
if(currentValue != previousValue) {
previousValue = currentValue;
alert("Value changed!");
}
});
Another option is to only trigger your changed function on certain keys. Use e.KeyCode to figure out what key was pressed.

You can also store the initial value in a data attribute and check it against the current value.
<input type="text" name="somename" id="id_someid" value="" data-initial="your initial value" />
$("#id_someid").keyup(function() {
return $(this).val() == $(this).data().initial;
});
Would return true if the initial value has not changed.

function checkChange($this){
var value = $this.val();
var sv=$this.data("stored");
if(value!=sv)
$this.trigger("simpleChange");
}
$(document).ready(function(){
$(this).data("stored",$(this).val());
$("input").bind("keyup",function(e){
checkChange($(this));
});
$("input").bind("simpleChange",function(e){
alert("the value is chaneged");
});
});
here is the fiddle http://jsfiddle.net/Q9PqT/1/

You can employ the use of data in jQuery and catch all of the events which then tests it against it's last value (untested):
$(document).ready(function() {
$("#fieldId").bind("keyup keydown keypress change blur", function() {
if ($(this).val() != jQuery.data(this, "lastvalue") {
alert("changed");
}
jQuery.data(this, "lastvalue", $(this).val());
});
});
This would work pretty good against a long list of items too. Using jQuery.data means you don't have to create a javascript variable to track the value. You could do $("#fieldId1, #fieldId2, #fieldId3, #fieldId14, etc") to track many fields.
UPDATE: Added blur to the bind list.

I had to use this kind of code for a scanner that pasted stuff into the field
$(document).ready(function() {
var tId,oldVal;
$("#fieldId").focus(function() {
oldVal = $("#fieldId").val();
tId=setInterval(function() {
var newVal = $("#fieldId").val();
if (oldVal!=newVal) oldVal=newVal;
someaction() },100);
});
$("#fieldId").blur(function(){ clearInterval(tId)});
});
Not tested...

I don't think there's a 'simple' solution. You'll probably need to use both the events onKeyUp and onChange so that you also catch when changes are made with the mouse. Every time your code is called you can store the value you've 'seen' on this.seenValue attached right to the field. This should make a little easier.

You can set events on a combination of key and mouse events, and onblur as well, to be sure. In that event, store the value of the input. In the next call, compare the current value with the lastly stored value. Only do your magic if it has actually changed.
To do this in a more or less clean way:
You can associate data with a DOM element (lookup api.jquery.com/jQuery.data ) So you can write a generic set of event handlers that are assigned to all elements in the form. Each event can pass the element it was triggered by to one generic function. That one function can add the old value to the data of the element. That way, you should be able to implement this as a generic piece of code that works on your whole form and every form you'll write from now on. :) And it will probably take no more than about 20 lines of code, I guess.
An example is in this fiddle: http://jsfiddle.net/zeEwX/

Since the user can go into the OS menu and select paste using their mouse, there is no safe event that will trigger this for you. The only way I found that always works is to have a setInterval that checks if the input value has changed:
var inp = $('#input'),
val = saved = inp.val(),
tid = setInterval(function() {
val = inp.val();
if ( saved != val ) {
console.log('#input has changed');
saved = val;
},50);
You can also set this up using a jQuery special event.

focus doesn't work in IE

i have the following function
function change()
{
var input = document.getElementById('pas');
var input2 = input.cloneNode(false);
input2.type = 'password';
input.parentNode.replaceChild(input2,input);
input2.focus();
}
but focus() doesn't work in ie7, so what can i do!
i want to have the cursor inside of input!
thanks
update
great solution, thanks, but now it doesn't work in opera:(

For IE you need to use a settimeout function due to it being lazy, for example:
setTimeout(function() { document.getElementById('myInput').focus(); }, 10);
From http://www.mkyong.com/javascript/focus-is-not-working-in-ie-solution/
For opera, this may help:
how to set focus in required index on textbox for opera
UPDATE:
The following snippet of code handles the case when the element is unavailable and retries after a short period - perfect for slow loading pages and/or elements not available until some time after.
setTimeout(
function( ) {
var el = document.getElementById( "myInput" ) ;
( el != null ) ? el.focus( ) : setTimeout( arguments.callee , 10 ) ;
}
, 10 ) ;

We hit the same issue. For focusing we are using General function which is applying settimeout solution mentioned in:
http://www.mkyong.com/javascript/focus-is-not-working-in-ie-solution/
with 100 milliseconds.
Still on some screens it's not working properly. Especially when iframes are included.
There is another known and similar IE issue:
IE 9 and IE 10 cannot enter text into input text boxes from time to time ->
IE 9 and IE 10 cannot enter text into input text boxes from time to time
What I have noticed is when you have focus, without pointer, you can apply workaround by pressing TAB key (focus on next element) and than SHIFT+TAB which will return to our target element with focus and typing pointer.
In order to be sure we can type inside input we focus on random element and then on our target input.
$('body').focus();
n.focus();
So we applied the same solution in javascript/JQuery in our general focus function.
So there is an if statement
...
if($.browser.msie) {
setTimeout(function() { try {
$('body').focus(); //First focus on random element
$(n).focus(); //Now focus on target element
} catch (e) { /*just ignore */ } }, 100); //See http://www.mkyong.com/javascript/focus-is-not-working-in-ie-solution/
} else { //Standard FF, Chrome, Safari solution...
...
To be sure since there is big regression we are still keeping solution with settimeout as a backup.
Tested on IE10, IE11, Firefox 45, Chrome 49.0.2623.87

IE7 does not support the focus() method. I don't see any method.

I've had the same issue and was able to get IE to work using code behind by making a SetInitialFocus function and calling it in my PageLoad function.
Take a look at the following example and give it a shot, it worked for me.
http://www.cambiaresearch.com/c4/df9f071c-a9eb-4d82-87fc-1a66bdcc068e/Set-Initial-Focus-on-an-aspnet-Page.aspx

function change() {
var input = document.getElementById('pas');
var input2 = input.cloneNode(false);
input2.type = 'password';
input.parentNode.replaceChild(input2, input);
setTimeout(function () {
input2.focus();
}, 10);
}

In Case you are looking to set focus in 1st input element of last row in table.Name of my div where i have kept my table is tableDiv and i am setting focus to last row's 1st inputtext
setTimeout(function(){
$($('#tableDiv tr:last').find('input[type=text]')[0]).focus();
},2);

#Bojan Tadic THANK YOU!
Below Code did the trick :)
$('body').focus(); //First focus on random element
I think the issue comes up when you use input and a placeholder. Managed so solved this thanks to this answer, I was missing that $(body).focus. Made this code to run only on IE so that all my inputs can be freely accessed by 'tabbing'. Previously when I had only tabIndex on my inputs I was able to move to the next one but focus wasn't complete and couldn't write anything in it.
This is complete code.
$('input[name^="someName"]').on('keydown', function(e){
var keyCode = e.which || e.keyCode;
if(keyCode === 9){
e.preventDefault();
$('body').focus();
var nextTabIndex = parseInt($(this).attr("tabIndex"));
nextTabIndex++;
setTimeout(function(){$('input[tabIndex=' + nextTabIndex +']')[0].focus();},20);
}
});

Its is very easy using jQuery, not sure why you are doing it the hard way :)
In this example I have a class assigned to the input field I want the initial focus set called initFocus. You can use any selector you want to find your element. from your code I would use $("#pas").focus();
$(".initFocus").focus();