Javascript event that fires without user interaction? - javascript

A textbox on my form may change depending on what's selected in various drop down lists.
Is there a way to call a javascript function when the textbox value changes?
Tried onchange event but this only seems to work if a user manually changes the textbox value.
Cheers,
Breandán

No, javascript-triggered changes to form elements don't trigger events. If they did, this would cause all sorts of recursive infinite loops.
The simple solution is to call your onchange function manually whenever you change the value of the textbox, however you could also use some kind of wrapper function. As a very basic example:
function updateTextField(new_text) {
text_field.value = new_text;
text_field.onchange();
}

When setting the content of the text box from your JS code, call out to another function passing in the text to set, you can then call it from where ever you need and do your logic then.

Try to disconnect the logic responsible for changing the control's value from the onchange event's execution path using a setTimeout.
<html>
<head>
<script type="text/javascript">
function setValue(target) {
alert("changed - value: " + target.value);
setTimeout("reallySetValue('" + target.id + "');", 1);
}
function reallySetValue(id) {
var control = document.getElementById(id);
control.value += control.value;
}
</script>
</head>
<body>
<form>
<div>
Enter "a" here:
<input type="text" id="test" onchange="setValue(this)">
<br/>
<br/>
<input type="text">
</div>
</form>
</body>
</html>
It's illustrated here
Changing a Textbox Value in its OnChange Event

In web browsers, programmatic changes on a control won't trigger events on that control. You must instruct the code that changes the textbox value to trigger the onchange event. This is how you can do it in plain javascript:
var textbox = document.getElementById("boxId");
textbox.value = "Abc";
textbox.onchange();
Of course, using a library like jQuery makes it easier and more robust:
$("#boxId").val("Abc").change();

You can use the excellent event.simulate.js to do this. This script does depend on the Prototype.js library, though.
If you'd want to this without relying on an external library, take a look at the fireEvent and createEvent functions. A simple demonstration of how you could implement this:
function triggerEvent(element, eventName)
{
if (document.createEvent)
{
var evt = document.createEvent('HTMLEvents');
evt.initEvent(eventName, true, true);
return element.dispatchEvent(evt);
}
if (element.fireEvent)
return element.fireEvent('on' + eventName);
}
triggerEvent(document.getElementById('myTextbox', 'change'));
Using event.simululate.js, you would do it like this:
Event.simulate('myTextbox', 'change');
A similiar question was asked here: Trigger an event with Prototype.
EDIT: although it is possible to use document.getElementById('myTextbox').change(), I would not recommend doing it, as it makes your code less flexible. When attaching onChange events to the textbox, these would not trigger when manually calling the change() event. Using the above method, events will propagate, just as if the event was a user-triggered one.

Assuming the frontend is in html:
You could install a timout callback and query the contents of the textbox in intervals of, say, 100msecs and compare it to some previous value you store in a variable.
Keywords: window.setTimout(), window.setInterval()

I'd recommend to look over YUI's Custom events for Example:
YUI Custom Event Example Link
All you need is to attach this script with Events manipulations
<script type="text/javascript" src="http://yui.yahooapis.com/2.7.0/build/yahoo-dom-event/yahoo-dom-event.js"></script>
and then you are able to use Custom Events (everywhere in HTML)
fnSubscriberChange - inside this Func you could do whatever you want. You could put your textbox change value logic here and depend on the Changed Select box value - call desired func.
Logic that depends on Event listening is clear and easy to modify;
YUI library supports all browsers so you shouldnt mind about browsers features.
Text box and select boxes:
<input type='text' id='id_text_fld' value=''/>
<select id='id_sel_one'>
<option value="test1">Test1
<option value="test2">Test2
</select>
<select id='id_sel_two'>
<option value="test3">Test3
<option value="test4">Test4
</select>
Script for events:
<script>
(function() {
//create a new custom event, to be fired
var onChangeValue = new YAHOO.util.CustomEvent("onChangeValue");
// Attach change event listener for Select boxes by their IDs
YAHOO.util.Event.on( ['id_sel_one', 'id_sel_two'], 'change', fnCallback, this);
// Function to call when Change event on Select occures
fnCallback = function(e) {
alert("This elem:" + this.id+ " changed value to:" + this.value);
// Fire our Custom event
onChangeValue.fire({dom_el: this}); // passing select box element [this] to function
}
// Listen for Custom event and call our Func
onChangeValue.subscribe(fnSubscriberChange); // Lets listen for ChangeValue event and call our Func
fnSubscriberChange = function(type, args) {
alert("Event type:" + type + " dom el id:" + args[0].dom_el.id );
var dom_el = args[0].dom_el; // Select Box that produces Change
};
})();
</script>

Related

what is the best jsript event handler to use when data is change through other script for select? [duplicate]

The logic in the change() event handler is not being run when the value is set by val(), but it does run when user selects a value with their mouse. Why is this?
<select id="single">
<option>Single</option>
<option>Single2</option>
</select>
<script>
$(function() {
$(":input#single").change(function() {
/* Logic here does not execute when val() is used */
});
});
$("#single").val("Single2");
</script>
Because the change event requires an actual browser event initiated by the user instead of via javascript code.
Do this instead:
$("#single").val("Single2").trigger('change');
or
$("#single").val("Single2").change();
I believe you can manually trigger the change event with trigger():
$("#single").val("Single2").trigger('change');
Though why it doesn't fire automatically, I have no idea.
Adding this piece of code after the val() seems to work:
$(":input#single").trigger('change');
As far as I can read in API's. The event is only fired when the user clicks on an option.
http://api.jquery.com/change/
For select boxes, checkboxes, and
radio buttons, the event is fired
immediately when the user makes a
selection with the mouse, but for the
other element types the event is
deferred until the element loses
focus.
To make it easier, add a custom function and call it whenever you want to change the value and also trigger a change:
$.fn.valAndTrigger = function (element) {
return $(this).val(element).trigger('change');
}
and
$("#sample").valAndTrigger("NewValue");
Or you can override the val() function to always call the change when val() is called:
(function ($) {
var originalVal = $.fn.val;
$.fn.val = function (value) {
this.trigger("change");
return originalVal.call(this, value);
};
})(jQuery);
Sample at http://jsfiddle.net/r60bfkub/
In case you don't want to mix up with default change event you can provide your custom event
$('input.test').on('value_changed', function(e){
console.log('value changed to '+$(this).val());
});
to trigger the event on value set, you can do
$('input.test').val('I am a new value').trigger('value_changed');
If you've just added the select option to a form and you wish to trigger the change event, I've found a setTimeout is required otherwise jQuery doesn't pick up the newly added select box:
window.setTimeout(function() { jQuery('.languagedisplay').change();}, 1);
I ran into the same issue while using CMB2 with Wordpress and wanted to hook into the change event of a file upload metabox.
So in case you're not able to modify the code that invokes the change (in this case the CMB2 script), use the code below.
The trigger is being invoked AFTER the value is set, otherwise your change eventHandler will work, but the value will be the previous one, not the one being set.
Here's the code i use:
(function ($) {
var originalVal = $.fn.val;
$.fn.val = function (value) {
if (arguments.length >= 1) {
// setter invoked, do processing
return originalVal.call(this, value).trigger('change');
}
//getter invoked do processing
return originalVal.call(this);
};
})(jQuery);
$(":input#single").trigger('change');
This worked for my script. I have 3 combos & bind with chainSelect event, I need to pass 3 values by url & default select all drop down. I used this
$('#machineMake').val('<?php echo $_GET['headMake']; ?>').trigger('change');
And the first event worked.
To change the value
$("#single").val("Single2");
Also to trigger a change event
$("#single").val("Single2").change();
this logic is instrumental when multiple select options are on a page.
one changes and other select options have to change but do not trigger a change event.

jQuery fire event if input is changed through Javascript

I need to fire an event if the input text has changed through Javascript using .val(), from jQuery API (https://api.jquery.com/change/): Note: Changing the value of an input element using JavaScript, using .val() for example, won't fire the event.
Have tried this How can I trigger an onchange event manually? but doesn't seem to work...
This is my code:
<input type="text" id="datePrint" maxlength="10" size="6" disabled>
<img src="scripts/calendar/calendar.png" id="datePick" border="0" align="absmiddle" alt="Pick Date" width="40px" height="40px">
JS: need to activate calendar events
Calendar.setup({inputField:'datePrint',ifFormat:'%d/%m/%Y',button:'datePick',align:'T1',singleClick:true});
And this is the calendar JS:
http://www.mediafire.com/view/yfrls2nx4m6ls52/calendarJs.txt
You can always trigger the change event while changing the input value.
$("input#id").trigger('change');
There are two ways. The simple answer is remember that every-time you use .val() to also call .change().
However, this begs the question on whether the DOM is the best place to keep state information. A more complex but flexible solution is to create a model/view object to store state and let it manage the events and updates.
However, upon further inspection on the comments the actual problem your attempting to address is not how to trigger change events but how to tell when an input has changed when another third party lib has pragmatically changed it.
The first step is to investigate the library in question and see if they provide a change event you can attach to. If not (after considering a different better behaved library), you are probably stuck with a polling solution.
function InputChangePoller(selector) {
this.el = $(selector);
this._lastKnownValue = this.el.val();
}
InputChangePoller.prototype.start = function() {
this._timmer = setImmediate($.proxy(this, 'checkValue'), 10);
return this;
};
InputChangePoller.prototype.stop = function() {
clearImmediate(this._timmer);
return this;
};
InputChangePoller.prototype.checkValue = function() {
var value = this.el.val();
if (value !== this._lastKnownValue) {
this._lastKnownValue = value;
this.el.trigger('change', value);
}
};

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
})

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