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Run a javascript function as user is inputting

I don't usually like to bother you all but I'm stuck on something and I can't find an answer anywhere, hope you guys can help me out!
I'm building a web app and designing it so the interface matches iOS7.
http://danj.eu/webdesign/new
I've got an input form, and I need the button to submit the form to only turn blue and become selectable once the validation has completed. I've wrote some JS to validate the input but this only runs once! I need to run the function every time the user modifies the value of the input.
This is what I've got so far for the JS:
function validateInput(){
if (document.getElementById('projectname').value.length < 2)
document.getElementById('forwardbutton').style.color = "#c4c4c5";
else
document.getElementById('forwardbutton').style.color = "#0e81ff";
}
Thanks guys!

add to your input onchange listener:
var input = document.getElementById("myInput");
input.addEventListener('change', validateInput, false);
this will fire validateInput function every time the value changes.
PS. you should cache your DOM elements that you get in your validation function, because it's searching through the DOM to find them always when function is fired- this can be heavy in a big DOM tree

jsFiddle Demo
You can bind to the input event using jquery which handles virtually all input events simultaneously
<input id="myInput" type="text" />
<div id="output"></div>
js
$('#myInput').bind('input',function(){
if( this.value.length < 2 ){
document.getElementById('output').style.color = "#c4c4c5";
}else{
document.getElementById('output').style.color = "#0e81ff";
}
$('#output').html(this.value);
});

I do not know if you are opposed to jQuery, but I'll provide the jQuery way of doing this. It's very simple with jQuery. You'd use a keyboard event handler, specifically the Key Up event handler.
In your event handler, you'd then check the length of the field and based on the length you would set the enabled or disabled state of the button.
$('#input-element').keyup(function () {
if (document.getElementById('projectname').value.length < 2)
document.getElementById('forwardbutton').style.color = "#c4c4c5";
else
document.getElementById('forwardbutton').style.color = "#0e81ff";
}
});
You can also use jQuery to set the color or enabled state as well, instead of your previous code. Up to you.

Do you mean
function validateInput(){
if (document.getElementById('projectname').value.length < 2)
document.getElementById('forwardbutton').style.color = "#c4c4c5";
else
document.getElementById('forwardbutton').style.color = "#0e81ff";
}
and then perhaps this?
document.getElementById('projectname').onchange=validateInput;
More information would be helpful.

How do I properly capture an onchange or onkeyup event for a dynamically inserted 'input' text element?

I have a bit of JavaScript that builds some HTML for me and inserts it into a div. I am using jQuery 1.7.2 for this test.
I'm interested in attaching a custom change or keyup event handler on an input text field called gene_autocomplete_field.
Here's what I have tried so far.
The following function builds the HTML, which is inserted into a div called gene_container:
function buildGeneContainerHTML(count, arr) {
var html = "";
// ...
html += "<input type='text' size='20' value='' id='gene_autocomplete_field' name='gene_autocomplete_field' placeholder='Enter gene name...' /><br/>";
// ...
return html;
}
// ...
$('#gene_container').html( buildGeneContainerHTML(count, geneNameArr) );
In my calling HTML, I grab the gene_autocomplete_field from the gene_container element, and then I override the keyup event handler for gene_autocomplete_field:
<script>
$(document).ready(function() {
$("#gene_container input:[name=gene_autocomplete_field]").live('keyup', function(event) {
refreshGenePicker($("#gene_container input:[name=gene_autocomplete_field]").val());
});
});
</script>
When I change the text in gene_autocomplete_field, the refreshGenePicker() function just sends an alert:
function refreshGenePicker(val) {
alert(val);
}
Result
If I type any letter into the gene_autocomplete_field element, the event handler seems to call alert(val) an infinite number of times. I get one alert after another and the browser gets taken over by the dialog boxes. The value returned is correct, but I worry that refreshGenePicker() gets called over and over again. This is not correct behavior, I don't think.
Questions
How do I properly capture the keyup event once, so that I only handle a content change to the autocomplete field the one time?
Is there a different event I should use for this purpose?
UPDATE
It turns out that more than just a keyCode of 13 (Return/Enter) can be an issue — pressing Control, Alt, Esc or other special characters will trigger an event (but will be asymptomatic, as far as the infinite loop issue goes). The gene names I am filtering on do not have metacharacters in them. So I made use of an alphanumeric detection test to filter out non-alphanumeric characters from further event handling, which includes the Return key:
if (!alphaNumericCheck(event.keyCode)) return;

alert is called infinite times because you use the 'Enter' key to confirm/dismiss the alert. Use .on('change') instead. This will prevent refreshGenePicker from being called when you use enter in an alert.
JSFiddle demonstration using keyup (Click on OK to prevent infinite alerts).
JSFiddle demonstration using change
However, the 'change' event will only trigger if the input element looses focus. If you want to use refreshGenePicker on every key, use the following approach instead:
$("#gene_container input:[name=gene_autocomplete_field]").live('keyup', function(event) {
if(event.keyCode === 13) // filter ENTER
return;
refreshGenePicker($("#gene_container input:[name=gene_autocomplete_field]").val());
});
This will filter any incoming enter keyup events (jsFiddle demo). Also switch to .on and drop .live.
EDIT: Note that there are more possibilities to dismiss an alert modal, such as the escape or space key. You should add a check inside your refreshGenePicker whether the value has actually changed.

You should really use .on() if you are using jQuery > 1.7.
Check out the perftest.
And also check out my some what related question.
Also when testing equal you should really add quotes around it:
input:[name='gene_autocomplete_field']
To answer you real question :). It shouldn;t behave like that with the code you have presented. Maybe something else is wrong. Can you setup a jsfiddle with the issue?
Check out my demo and perhaps you see what's wrong with your code:
function refreshGenePicker(value) {
console.log('keyup! Value is now: ' + value);
}
(function($) {
var someHtml = '<input type="text" name="gene_autocomplete_field">';
$('body').append(someHtml);
$('body').on('keyup', 'input[name="gene_autocomplete_field"]', function(e) {
refreshGenePicker($(this).val());
});
})(jQuery);​

$(document).ready(function() {
$('#test').html('<input id="text" />');
$('#text').keyup(function() {
console.log($(this).val());
});
});​
This works just fine. Since you've got our second code block in <script> tags, you might be running it more than once - which would cause it to bind more than once and produce more than one alert each time it is bound. You could of course use .unbind() on that input before adding the keyup, but I think a much better solution would be to group all the code in a single $(document).ready(); to ensure you're only binding the object once.
http://jsfiddle.net/Ka7Ty/2/

Any event triggered on autocomplete?

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 to detect a textbox's content has changed

I want to detect whenever a textbox's content has changed. I can use the keyup method, but that will also detect keystrokes which do not generate letters, like the arrow keys. I thought of two methods of doing this using the keyup event:
Check explictly if the ascii code of the pressed key is a letter\backspace\delete
Use closures to remember what was the text in the textbox before the key stroke and check whether this has changed.
Both look kinda cumbersome.

Start observing 'input' event instead of 'change'.
jQuery('#some_text_box').on('input', function() {
// do your stuff
});
...which is nice and clean, but may be extended further to:
jQuery('#some_text_box').on('input propertychange paste', function() {
// do your stuff
});

Use the onchange event in HTML/standard JavaScript.
In jQuery that is the change() event. For example:
$('element').change(function() { // do something } );
EDIT
After reading some comments, what about:
$(function() {
var content = $('#myContent').val();
$('#myContent').keyup(function() {
if ($('#myContent').val() != content) {
content = $('#myContent').val();
alert('Content has been changed');
}
});
});

The 'change' event doesn't work correctly, but the 'input' is perfect.
$('#your_textbox').bind('input', function() {
/* This will be fired every time, when textbox's value changes. */
} );

How about this:
< jQuery 1.7
$("#input").bind("propertychange change keyup paste input", function(){
// do stuff;
});
> jQuery 1.7
$("#input").on("propertychange change keyup paste input", function(){
// do stuff;
});
This works in IE8/IE9, FF, Chrome

Use closures to remember what was the text in the checkbox before the key stroke and check whether this has changed.
Yep. You don't have to use closures necessarily, but you will need to remember the old value and compare it to the new.
However! This still won't catch every change, because there a ways of editing textbox content that do not involve any keypress. For example selecting a range of text then right-click-cut. Or dragging it. Or dropping text from another app into the textbox. Or changing a word via the browser's spell-check. Or...
So if you must detect every change, you have to poll for it. You could window.setInterval to check the field against its previous value every (say) second. You could also wire onkeyup to the same function so that changes that are caused by keypresses are reflected quicker.
Cumbersome? Yes. But it's that or just do it the normal HTML onchange way and don't try to instant-update.

$(document).on('input','#mytxtBox',function () {
console.log($('#mytxtBox').val());
});
You can use 'input' event to detect the content change in the textbox. Don't use 'live' to bind the event as it is deprecated in Jquery-1.7, So make use of 'on'.

I assume that you are looking to do something interactive when the textbox changes (i.e. retrieve some data via ajax). I was looking for this same functionality. I know using a global isn't the most robust or elegant solution, but that is what I went with. Here is an example:
var searchValue = $('#Search').val();
$(function () {
setTimeout(checkSearchChanged, 0.1);
});
function checkSearchChanged() {
var currentValue = $('#Search').val();
if ((currentValue) && currentValue != searchValue && currentValue != '') {
searchValue = $('#Search').val();
$('#submit').click();
}
else {
setTimeout(checkSearchChanged, 0.1);
}
}
One key thing to note here is that I am using setTimeout and not setInterval since I don't want to send multiple requests at the same time. This ensures that the timer "stops" when the form is submitted and "starts" when the request is complete. I do this by calling checkSearchChanged when my ajax call completes. Obviously you could expand this to check for minimum length, etc.
In my case, I am using ASP.Net MVC so you can see how to tie this in with MVC Ajax as well in the following post:
http://geekswithblogs.net/DougLampe/archive/2010/12/21/simple-interactive-search-with-jquery-and-asp.net-mvc.aspx

I would recommend taking a look at jQuery UI autocomplete widget. They handled most of the cases there since their code base is more mature than most ones out there.
Below is a link to a demo page so you can verify it works. http://jqueryui.com/demos/autocomplete/#default
You will get the most benefit from reading the source and seeing how they solved it. You can find it here: https://github.com/jquery/jquery-ui/blob/master/ui/jquery.ui.autocomplete.js.
Basically they do it all, they bind to input, keydown, keyup, keypress, focus and blur. Then they have special handling for all sorts of keys like page up, page down, up arrow key and down arrow key. A timer is used before getting the contents of the textbox. When a user types a key that does not correspond to a command (up key, down key and so on) there is a timer that explorers the content after about 300 milliseconds. It looks like this in the code:
// switch statement in the
switch( event.keyCode ) {
//...
case keyCode.ENTER:
case keyCode.NUMPAD_ENTER:
// when menu is open and has focus
if ( this.menu.active ) {
// #6055 - Opera still allows the keypress to occur
// which causes forms to submit
suppressKeyPress = true;
event.preventDefault();
this.menu.select( event );
}
break;
default:
suppressKeyPressRepeat = true;
// search timeout should be triggered before the input value is changed
this._searchTimeout( event );
break;
}
// ...
// ...
_searchTimeout: function( event ) {
clearTimeout( this.searching );
this.searching = this._delay(function() { // * essentially a warpper for a setTimeout call *
// only search if the value has changed
if ( this.term !== this._value() ) { // * _value is a wrapper to get the value *
this.selectedItem = null;
this.search( null, event );
}
}, this.options.delay );
},
The reason to use a timer is so that the UI gets a chance to be updated. When Javascript is running the UI cannot be updated, therefore the call to the delay function. This works well for other situations such as keeping focus on the textbox (used by that code).
So you can either use the widget or copy the code into your own widget if you are not using jQuery UI (or in my case developing a custom widget).

do you consider using change event ?
$("#myTextBox").change(function() { alert("content changed"); });

I'd like to ask why you are trying to detect when the content of the textbox changed in real time?
An alternative would be to set a timer (via setIntval?) and compare last saved value to the current one and then reset a timer. This would guarantee catching ANY change, whether caused by keys, mouse, some other input device you didn't consider, or even JavaScript changing the value (another possiblity nobody mentioned) from a different part of the app.

Use the textchange event via customized jQuery shim for cross-browser input compatibility. http://benalpert.com/2013/06/18/a-near-perfect-oninput-shim-for-ie-8-and-9.html (most recently forked github: https://github.com/pandell/jquery-splendid-textchange/blob/master/jquery.splendid.textchange.js)
This handles all input tags including <textarea>content</textarea>, which does not always work with change keyup etc. (!) Only jQuery on("input propertychange") handles <textarea> tags consistently, and the above is a shim for all browsers that don't understand input event.
<!DOCTYPE html>
<html>
<head>
<script class="jsbin" src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script src="https://raw.githubusercontent.com/pandell/jquery-splendid-textchange/master/jquery.splendid.textchange.js"></script>
<meta charset=utf-8 />
<title>splendid textchange test</title>
<script> // this is all you have to do. using splendid.textchange.js
$('textarea').on("textchange",function(){
yourFunctionHere($(this).val()); });
</script>
</head>
<body>
<textarea style="height:3em;width:90%"></textarea>
</body>
</html>
JS Bin test
This also handles paste, delete, and doesn't duplicate effort on keyup.
If not using a shim, use jQuery on("input propertychange") events.
// works with most recent browsers (use this if not using src="...splendid.textchange.js")
$('textarea').on("input propertychange",function(){
yourFunctionHere($(this).val());
});

There's a complete working example here.
<html>
<title>jQuery Summing</title>
<head>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"> </script>
$(document).ready(function() {
$('.calc').on('input', function() {
var t1 = document.getElementById('txt1');
var t2 = document.getElementById('txt2');
var tot=0;
if (parseInt(t1.value))
tot += parseInt(t1.value);
if (parseInt(t2.value))
tot += parseInt(t2.value);
document.getElementById('txt3').value = tot;
});
});
</script>
</head>
<body>
<input type='text' class='calc' id='txt1'>
<input type='text' class='calc' id='txt2'>
<input type='text' id='txt3' readonly>
</body>
</html>

Something like this should work, mainly because focus and focusout would end up with two separate values. I'm using data here because it stores values in the element but doesn't touch the DOM. It is also an easy way to store the value connected to its element. You could just as easily use a higher-scoped variable.
var changed = false;
$('textbox').on('focus', function(e) {
$(this).data('current-val', $(this).text();
});
$('textbox').on('focusout', function(e) {
if ($(this).data('current-val') != $(this).text())
changed = true;
}
console.log('Changed Result', changed);
}

This Code detects whenever a textbox's content has changed by the user and modified by Javascript code.
var $myText = jQuery("#textbox");
$myText.data("value", $myText.val());
setInterval(function() {
var data = $myText.data("value"),
val = $myText.val();
if (data !== val) {
console.log("changed");
$myText.data("value", val);
}
}, 100);

document.getElementById('txtrate' + rowCount).onchange = function () {
// your logic
};
This one works fine but triggers the event on click too which is not good. my system went into loop.
while
$('#txtrate'+rowCount).bind('input', function() {
//your logic
} );
works perfectly in my scenario. it only works when value is changed.
instead of $ sign one can use document.getElementById too

Detect all changes to a <input type="text"> (immediately) using JQuery

There are many ways the value of a <input type="text"> can change, including:
keypresses
copy/paste
modified with JavaScript
auto-completed by browser or a toolbar
I want my JavaScript function to be called (with the current input value) any time it changes. And I want it to be called right away, not just when the input loses focus.
I'm looking for the cleanest and most robust way to do this across all browsers (using jQuery preferably).

This jQuery code uses .bind() to catch immediate changes to any element, and should work across all browsers:
$('.myElements').each(function() {
var elem = $(this);
// Save current value of element
elem.data('oldVal', elem.val());
// Look for changes in the value
elem.bind("propertychange change click keyup input paste", function(event){
// If value has changed...
if (elem.data('oldVal') != elem.val()) {
// Updated stored value
elem.data('oldVal', elem.val());
// Do action
....
}
});
});
However, note that .bind() was deprecated in jQuery version 3.0. Anyone using jQuery version 1.7 or newer should use .on() instead.

A real-time solution for jQuery >= 1.7 is on
$("#input-id").on("change keyup paste", function(){
dosomething();
})
if you also want to detect "click" event, just:
$("#input-id").on("change keyup paste click", function(){
dosomething();
})
if you're using jQuery <= 1.6, just use bind or live instead of on.

Unfortunately, I think setInterval wins the prize:
<input type=text id=input_id />
<script>
setInterval(function() { ObserveInputValue($('#input_id').val()); }, 100);
</script>
It's the cleanest solution, at only 1 line of code. It's also the most robust, since you don't have to worry about all the different events/ways an input can get a value.
The downsides of using 'setInterval' don't seem to apply in this case:
The 100ms latency? For many applications, 100ms is fast enough.
Added load on the browser? In general, adding lots of heavy-weight setIntervals on your page is bad. But in this particular case, the added page load is undetectable.
It doesn't scale to many inputs? Most pages don't have more than a handful of inputs, which you can sniff all in the same setInterval.

Binding to the input event seems to work fine in most sane browsers. IE9 supports it too, but the implementation is buggy (the event is not fired when deleting characters).
With jQuery version 1.7+ the on method is useful to bind to the event like this:
$(".inputElement").on("input", null, null, callbackFunction);

Unfortunately there is no event or set of events that matches your criteria. Keypresses and copy/paste can both be handled with the keyup event. Changes through JS are trickier. If you have control over the code that sets the textbox, your best bet is to modify it to either call your function directly or trigger a user event on the textbox:
// Compare the textbox's current and last value. Report a change to the console.
function watchTextbox() {
var txtInput = $('#txtInput');
var lastValue = txtInput.data('lastValue');
var currentValue = txtInput.val();
if (lastValue != currentValue) {
console.log('Value changed from ' + lastValue + ' to ' + currentValue);
txtInput.data('lastValue', currentValue);
}
}
// Record the initial value of the textbox.
$('#txtInput').data('lastValue', $('#txtInput').val());
// Bind to the keypress and user-defined set event.
$('#txtInput').bind('keypress set', null, watchTextbox);
// Example of JS code triggering the user event
$('#btnSetText').click(function (ev) {
$('#txtInput').val('abc def').trigger('set');
});
If you don't have control over that code, you could use setInterval() to 'watch' the textbox for changes:
// Check the textbox every 100 milliseconds. This seems to be pretty responsive.
setInterval(watchTextbox, 100);
This sort of active monitoring won't catch updates 'immediately', but it seems to be fast enough that there is no perceptible lag. As DrLouie pointed out in comments, this solution probably doesn't scale well if you need to watch lots of inputs. You can always adjust the 2nd parameter to setInterval() to check more or less frequently.

Here is a solution that doesn't make use of jQuery (Its really quite obsolete and not necessary these days)
Using the event "input" you can look for any kind of change:
Deleting, Backspacing, Pasting, Typing, anything that will change the inputs value.
The input event is directly related to the text input. ANY time the text is changed in ANY fashion, input is dispatched.
document.querySelector("#testInput").addEventListener("input", test);
function test(e) {
var a = document.getElementById('output');
a.innerText += "Detected an Update!\n";
}
<input id="testInput">
<br>
<a id="output"></a>

Here is a slightly different solution if you didn't fancy any of the other answers:
var field_selectors = ["#a", "#b"];
setInterval(function() {
$.each(field_selectors, function() {
var input = $(this);
var old = input.attr("data-old-value");
var current = input.val();
if (old !== current) {
if (typeof old != 'undefined') {
... your code ...
}
input.attr("data-old-value", current);
}
}
}, 500);
Consider that you cannot rely on click and keyup to capture context menu paste.

Add this code somewhere, this will do the trick.
var originalVal = $.fn.val;
$.fn.val = function(){
var result =originalVal.apply(this,arguments);
if(arguments.length>0)
$(this).change(); // OR with custom event $(this).trigger('value-changed');
return result;
};
Found this solution at val() doesn't trigger change() in jQuery

I have created a sample. May it will work for you.
var typingTimer;
var doneTypingInterval = 10;
var finaldoneTypingInterval = 500;
var oldData = $("p.content").html();
$('#tyingBox').keydown(function () {
clearTimeout(typingTimer);
if ($('#tyingBox').val) {
typingTimer = setTimeout(function () {
$("p.content").html('Typing...');
}, doneTypingInterval);
}
});
$('#tyingBox').keyup(function () {
clearTimeout(typingTimer);
typingTimer = setTimeout(function () {
$("p.content").html(oldData);
}, finaldoneTypingInterval);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<textarea id="tyingBox" tabindex="1" placeholder="Enter Message"></textarea>
<p class="content">Text will be replace here and after Stop typing it will get back</p>
http://jsfiddle.net/utbh575s/

We actually don't need to setup loops for detecting javaScript changes.
We already setting up many event listeners to the element we want to detect. just triggering any un harmful event will make the job.
$("input[name='test-element']").on("propertychange change click keyup input paste blur", function(){
console.log("yeh thats worked!");
});
$("input[name='test-element']").val("test").trigger("blur");
and ofc this is only available if you have the full control on javascript changes on your project.

Although this question was posted 10 years ago, I believe that it still needs some improvements. So here is my solution.
$(document).on('propertychange change click keyup input paste', 'selector', function (e) {
// Do something here
});
The only problem with this solution is, it won't trigger if the value changes from javascript like $('selector').val('some value'). You can fire any event to your selector when you change the value from javascript.
$(selector).val('some value');
// fire event
$(selector).trigger('change');
Or in a single line
$(selector).val('some value').trigger('change');

Well, best way is to cover those three bases you listed by yourself. A simple :onblur, :onkeyup, etc won't work for what you want, so just combine them.
KeyUp should cover the first two, and if Javascript is modifying the input box, well I sure hope it's your own javascript, so just add a callback in the function that modifies it.

Here's a working example that I'm using to implement an autocomplete variation the populates a jqueryui selector (list), but I don't want it to function exactly like the jqueryui autocomplete which does a drop-down menu.
$("#tagFilter").on("change keyup paste", function() {
var filterText = $("#tagFilter").val();
$("#tags").empty();
$.getJSON("http://localhost/cgi-bin/tags.php?term=" + filterText,
function(data) {
var i;
for (i = 0; i < data.length; i++) {
var tag = data[i].value;
$("#tags").append("<li class=\"tag\">" + tag + "</li>");
}
});
});

Can't you just use <span contenteditable="true" spellcheck="false"> element in place of <input type="text">?
<span> (with contenteditable="true" spellcheck="false" as attributes) distincts by <input> mainly because:
It's not styled like an <input>.
It doesn't have a value property, but the text is rendered as innerText and makes part of its inner body.
It's multiline whereas <input> isn't although you set the attribute multiline="true".
To accomplish the appearance you can, of course, style it in CSS, whereas writing the value as innerText you can get for it an event:
Here's a fiddle.
Unfortunately there's something that doesn't actually work in IE and Edge, which I'm unable to find.

you can simply identify all changers in the form, like this
//when form change, show aleart
$("#FormId").change(function () {
aleart('Done some change on form');
});

You can bind the 'input' event to <input type="text">. This will trigger every time the input changes such as copy, paste, keypress, and so on.
$("#input-id").on("input", function(){
// Your action
})