How to test if onpropertychange is supported or not? - javascript

I'd like to know if an input element has changed, I learned that I can listen to onpropertychange in IE and oninput in other browsers.
Here is my code:
var _addChangedProperty = function(input){
input.changed = false;
var oninput = function(){
this.changed = !!this.value;
if(this.changed){
this.style.color = "black";
}
};
input.onpropertychange = input.oninput = oninput;
};
Now I'd like to change input.onpropertychange = input.oninput = oninput; to addEventListerner and attachEvent, I need to check if onpropertychange event is supported, how could I do this (without browser detect)?

You can check using the in operator:
"onpropertychange" in input
This kind of feature test doesn't work in older versions of Firefox, which report false event for event handler properties corresponding to events that do exist, but that isn't a problem here because Firefox doesn't currently support the propertychange event and is unlikely to in the future.
Here's some background: http://perfectionkills.com/detecting-event-support-without-browser-sniffing/
One other point: you need separate functions to handle the propertychange and input events, because in the propertychange handler you need to check whether it is the value property that has changed. Otherwise, you'll end up handling changes to any property of the input.
input.onpropertychange = function(evt) {
evt = evt || window.event;
if (evt.propertyName == "value") {
// Do stuff here
}
};

Related

Changing input value inside "input" event handler prevents "change" event firing in Chrome and IE (but not in Firefox)

In the following code I have "input" event handler that changes the value of the input as the user types. I also have "change" event handler to keep track of any changes made to this field. For some reason "change" event doesn't fire in Chrome and IE when the user leaves the field. Why is that and how to make it work in all major browsers?
Also note that it's not acceptable to trigger "change" event manually every time "input" event fires.
EDIT: "change" event seems to fire in Chrome only if transform function does not change the resulting string in any way. So if I type lower case letters and focus out after every character, "change" fires only for indexes 0, 2, 4 ...
Link to fiddle: http://jsfiddle.net/3hqxx2pr/
function transform(s) {
var r = "";
for (var i = 0; i < s.length; i++) {
r += i & 1 ? s[i].toUpperCase() : s[i];
}
return r;
}
$(document).ready(function(){
$("#in").on("change", function() {
console.log("changed"); // works only in ff
});
$("#in").on("input propertychange", function() {
$("#in").val(transform($("#in").val()));
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<input id="in"/>
Trigger change yourself
$("#in").val(transform($("#in").val())).change();
or
$("#in").val(transform($("#in").val())).trigger("change");
Based on a edit and restriction you made:
$("#in").on("input propertychange", function() {
var inp = $(this);
var orgVal = inp.val();
var transVal = transform(orgVal);
if (orgVal !== transVal) {
inp.val(transVal).trigger("change");
}
});

How do I fire a JavaScript event trigger?

I have an input using a onkeypress trigger, and I'm trying to find a way to fire the event trigger with a specific keycode. I've looked around but all I find are jQuery solutions, and I don't want to use jQuery.
For a click trigger you'd just use document.forms[0].elements[1].click() but there doesn't seem to be a keypress() equivalent for onkeypress.
You can create an event and dispatch it to your Object. just like this:
if(document.createEvent) {
var evObj = document.createEvent('KeyEvent');
evObj.initEvent( 'keypress', true, false);
evObj.keyCode = 13; // Set your keyCode
document.getElementById("myid").dispatchEvent(evObj);
}
under IE/FF:
var evObj = document.createEventObject();
evnObj.keyCode = 13;
document.getElementById("myid").fireEvent("onclick",evObj);
event.cancelBubble = true;

onchange event not fire when the change come from another function

I have an input text that get his value from a Javascript function (a timer with countdown).
I want to raise an event when the input text is 0 ,so I am using the change eventListener.
Unfortunately it doesn't seem to raise the event when the change is coming from javascript function.
How can I force the change event to work, even if the change is coming from Javascript and not from the user?
From the fine manual:
change
The change event occurs when a control loses the input focus and its value has been modified since gaining focus. This event is valid for INPUT, SELECT, and TEXTAREA. element.
When you modify the text input's value through code, the change event will not be fired because there is no focus change. You can trigger the event yourself though with createEvent and dispatchEvent, for example:
el = document.getElementById('x');
ev = document.createEvent('Event');
ev.initEvent('change', true, false);
el.dispatchEvent(ev);
And a live version: http://jsfiddle.net/ambiguous/nH8CH/
In the function that changes the value, manually fire a change event.
var e = document.createEvent('HTMLEvents');
e.initEvent('change', false, false);
some_input_element.dispatchEvent(e);
it's 2018 now and seems that initEvent() is deprecated:
https://developer.mozilla.org/en-US/docs/Web/API/Event/initEvent
i think you can trigger the event in a one-liner now:
element.dispatchEvent(new Event('change'));
A more reusable option :
function simulate_event(eventName, element) {
// You could set this into the prototype as a method.
var event;
if (document.createEvent) {
event = document.createEvent("HTMLEvents");
event.initEvent(eventName, true, true);
} else {
event = document.createEventObject();
event.eventType = eventName;
};
event.eventName = eventName;
if (document.createEvent) {
element.dispatchEvent(event);
} else {
element.fireEvent("on" + event.eventName, event);
}
};
Simply redefine the "value" property of the node, using getAttribute("value") and setAttribute("value", newValue), in the getters and setters, as well as dispatch the "change" event at the end of the setter. For example:
myNode.onchange = e => console.log("Changed!", e.target.value);
Object.defineProperty(myNode, "value", {
get: () => myNode.getAttribute("value"),
set(newValue) {
myNode.setAttribute("value", newValue);
myNode.dispatchEvent(new Event("change")); //or define the event earlier, not sure how much of a performance difference it makes though
}
})
var i = 0;
setTimeout(function changeIt() {
if(i++ < 10) {
myNode.value = i;
setTimeout(changeIt, 1000);
}
}, 1)
<input id="myNode">
Instead of using change, you can use keypress event instead.
This is because the change event is not meant to fire until it is not focused anymore - when you click out of the input tag.

Trigger a keypress/keydown/keyup event in JS/jQuery?

What is the best way to simulate a user entering text in a text input box in JS and/or jQuery?
I don't want to actually put text in the input box, I just want to trigger all the event handlers that would normally get triggered by a user typing info into a input box. This means focus, keydown, keypress, keyup, and blur. I think.
So how would one accomplish this?
You can trigger any of the events with a direct call to them, like this:
$(function() {
$('item').keydown();
$('item').keypress();
$('item').keyup();
$('item').blur();
});
Does that do what you're trying to do?
You should probably also trigger .focus() and potentially .change()
If you want to trigger the key-events with specific keys, you can do so like this:
$(function() {
var e = $.Event('keypress');
e.which = 65; // Character 'A'
$('item').trigger(e);
});
There is some interesting discussion of the keypress events here: jQuery Event Keypress: Which key was pressed?, specifically regarding cross-browser compatability with the .which property.
You could dispatching events like
el.dispatchEvent(new Event('focus'));
el.dispatchEvent(new KeyboardEvent('keypress',{'key':'a'}));
To trigger an enter keypress, I had to modify #ebynum response, specifically, using the keyCode property.
e = $.Event('keyup');
e.keyCode= 13; // enter
$('input').trigger(e);
Here's a vanilla js example to trigger any event:
function triggerEvent(el, type){
if ('createEvent' in document) {
// modern browsers, IE9+
var e = document.createEvent('HTMLEvents');
e.initEvent(type, false, true);
el.dispatchEvent(e);
} else {
// IE 8
var e = document.createEventObject();
e.eventType = type;
el.fireEvent('on'+e.eventType, e);
}
}
You can achieve this with: EventTarget.dispatchEvent(event) and by passing in a new KeyboardEvent as the event.
For example: element.dispatchEvent(new KeyboardEvent('keypress', {'key': 'a'}))
Working example:
// get the element in question
const input = document.getElementsByTagName("input")[0];
// focus on the input element
input.focus();
// add event listeners to the input element
input.addEventListener('keypress', (event) => {
console.log("You have pressed key: ", event.key);
});
input.addEventListener('keydown', (event) => {
console.log(`key: ${event.key} has been pressed down`);
});
input.addEventListener('keyup', (event) => {
console.log(`key: ${event.key} has been released`);
});
// dispatch keyboard events
input.dispatchEvent(new KeyboardEvent('keypress', {'key':'h'}));
input.dispatchEvent(new KeyboardEvent('keydown', {'key':'e'}));
input.dispatchEvent(new KeyboardEvent('keyup', {'key':'y'}));
<input type="text" placeholder="foo" />
MDN dispatchEvent
MDN KeyboardEvent
You're now able to do:
var e = $.Event("keydown", {keyCode: 64});
First of all, I need to say that sample from Sionnach733 worked flawlessly. Some users complain about absent of actual examples. Here is my two cents. I've been working on mouse click simulation when using this site: https://www.youtube.com/tv. You can open any video and try run this code. It performs switch to next video.
function triggerEvent(el, type, keyCode) {
if ('createEvent' in document) {
// modern browsers, IE9+
var e = document.createEvent('HTMLEvents');
e.keyCode = keyCode;
e.initEvent(type, false, true);
el.dispatchEvent(e);
} else {
// IE 8
var e = document.createEventObject();
e.keyCode = keyCode;
e.eventType = type;
el.fireEvent('on'+e.eventType, e);
}
}
var nextButton = document.getElementsByClassName('icon-player-next')[0];
triggerEvent(nextButton, 'keyup', 13); // simulate mouse/enter key press
For typescript cast to KeyboardEventInit and provide the correct keyCode integer
const event = new KeyboardEvent("keydown", {
keyCode: 38,
} as KeyboardEventInit);
I thought I would draw your attention that in the specific context where a listener was defined within a jQuery plugin, then the only thing that successfully simulated the keypress event for me, eventually caught by that listener, was to use setTimeout().
e.g.
setTimeout(function() { $("#txtName").keypress() } , 1000);
Any use of $("#txtName").keypress() was ignored, although placed at the end of the .ready() function. No particular DOM supplement was being created asynchronously anyway.

window.event.srcElement.options NOT Work on FF

window.event.srcElement.options(window.event.srcElement.selectedIndex).value works in Internet Explorer (and Chrome) but not in FireFox. How to make this work in FireFox as well?
event.target.options[event.target.selectedIndex].value. Though as always with events you'd have to have passed the event object into a function, so eg.:
<script>
function selectChanged(event) {
var target= event.target || event.srcElement;
doSomethingWith(target.options[target.selectedIndex].value);
};
</script>
<select onchange="selectChanged(event)">...</select>
Setting the handler directly and using this may be easier:
<select id="x">...</select>
<script>
document.getElementById('x').onchange= function() {
doSomethingWith(this.options[this.selectedIndex].value);
};
</script>
Note that looking at options[selectedIndex] is for compatibility with older browsers. These days you can usually just get away with saying select.value.
There is no global event object in Firefox. Events are passed to their handlers as an argument. Also, instead of srcElement, you look for target.
If you use a javascript library like jQuery, all the browser specific quirks are handled for you.
Otherwise, I suggest you to read these articles
http://www.quirksmode.org/js/introevents.html
http://www.quirksmode.org/js/events_properties.html
var addEvent = (function() {
function addEventIE(el, ev, fn) {
return el.attachEvent('on' + ev, function(e) {
return fn.call(el, e);
});
}
function addEventW3C(el, ev, fn) {
return el.addEventListener(ev, fn, false);
}
return window.addEventListener ? addEventW3C:addEventIE;
})();
var domRef = document.getElementById('foo');
addEvent( domRef, 'change', function(e) {
e = e || window.event;
var el = e.target ? e.target : e.srcElement,
value = el.value;
alert( value )
});
in IE, event is a property of window, in modern DOM supporting browsers it's passed as the first argument.
IE uses srcElement where most other browsers (including Firefox) use target.
Also, Firefox passes around event objects, whereas IE just populates the global event object w/the current event's data.
You'll have to handle both in your code. How you handle the 2nd one will depend on how you're assigning the handler.
But here's one way.
function changeHanlder( event )
{
var elem = event.target || event.srcElement;
alert( elem.options[elem.selectedIndex].value );
}
It's also worth noting that all the modern javascirpt libraries handle this abstraction for you.
There are two approaches:
Assume there is markup
<SELECT name="ddlQuery" id="ddlQuery" style="width:273px;"
onchange="GetDropDownValue(event)">
...
on HTML.
One using js function:
function GetDropDownValue(e)
{
var rtnVal = "";
var sel = document.getElementById(getTargetID(e));
for (var i = 0; i < sel.options.length; ++i) {
if (sel.options[i].selected == true) {
rtnVal = sel.options[i].value;
break;
}
}
alert(rtnVal);
return rtnVal;
}
function getTargetID(e) {
if (!e) { var e = window.event; }
var objTarget = e.srcElement ? e.srcElement : e.target;
return objTarget.id;
}
another using jQuery:
$('#ddlQuery').val()
Firefox uses e.htmlEvent.target.nodeName
you can use try/catch to handle both browsers.

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