I'm trying to find a way to detect changes to the element style but I haven't had much luck. The code below works on a new property I define like tempBgColor but I cannot override/shadow an existing property like color. I know jquery has a watch function, but it only detects changes from the jquery api but not directly changing the value of a style something like elem.style.color.
var e = document.getElementById('element');
e.style.__defineGetter__("color", function() {
return "A property";
});
e.style.__defineSetter__("color", function(val) {
alert("Setting " + val + "!");
});
Any pointers?
You should be able to do this with a MutationObserver - see demo (Webkit only), which is the new, shiny way of getting notified about changes in the DOM. The older, now deprecated, way was Mutation events.
Demo simply logs in the console the old and new values when the paragraph is clicked. Note that the old value will not be available if it was set via a non-inline CSS rule, but the change will still be detected.
HTML
<p id="observable" style="color: red">Lorem ipsum</p>
JavaScript
var MutationObserver = window.WebKitMutationObserver;
var target = document.querySelector('#observable');
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(mutation) {
console.log('old', mutation.oldValue);
console.log('new', mutation.target.style.cssText);
});
});
var config = { attributes: true, attributeOldValue: true }
observer.observe(target, config);
// click event to change colour of the thing we are observing
target.addEventListener('click', function(ev) {
observable.style.color = 'green';
return false;
}, false);
Credit to this blog post, for some of the code above.
With Chrome's Developer Tools open, you can find the element whose style's change you're interested in, right click it, select "Break on..." and "Attributes modifications".
here is a naive implementation using setTimeout with undescorejs.
The only way to find out which change was made is to iterate through the style object properties.
Here is the live example
$( function () {
var ele = document.getElementById('ele'),
oldStyle = {};
function checkEquality() {
style = _.clone(ele.style);
if (!_.isEqual(style, oldStyle)) {
console.log('Not equal');
oldStyle = _.clone(style);
} else {
console.log('Equal');
}
_.delay(checkEquality, 2000);
}
checkEquality();
$('a#add_prop').on('click', function () {
var props = $('#prop').val().replace(/ /g, '').split(':');
console.log(props);
$(ele).css(props[0], props[1]);
});
$('#prop').on('keydown', function (e) {
if (e.keyCode == 13) {
$('a#add_prop').trigger('click');
}
});
});
Related
I'm trying to get the focus method (touch, mouse or keyboard) on links setting a data-attribute.
$(function() {
var i,
r = document.getElementsByTagName("a")[0];
if ("ontouchstart" in window) {
document.addEventListener("touchstart", function(event) {
i = "touch";
}, true);
}
else {
document.addEventListener("mousedown", function(event) {
i = "mouse";
}, true);
}
document.addEventListener("keydown", function(event) {
i = "keyboard";
}, true);
})
The problem is that I only get results writing the last part in jQuery:
$("a").focus(function() {
$(this).attr("data-focus-method", i)
})
$("a").blur(function() {
$(this).removeAttr("data-focus-method")
})
And I want to write the whole code in plain JavaScript. I've tried the way below:
r.addEventListener("focus", function() {
r.setAttribute("data-focus-method", i);
});
r.addEventListener("blur", function() {
r.removeAttribute("data-focus-method");
});
But it doesn't work.
Can somebody help me please?
I suggest to use querySelectorAll method and use forEach to iterate the nodelist
document.querySelectorAll("a").forEach((link) => {
link.addEventListener("focus", function() {
this.setAttribute("data-focus-method", i);
});
link.addEventListener("blur", function() {
this.removeAttribute("data-focus-method");
});
});
I'm not sure why you're trying to override the i on method whenever a key is pressed on the keyboard. However, I'm assuming that's the desired effect since you don't mention it in your question.
That said, here's something to get you closer to your goal of a vanilla JS version of the code.
The answer uses the spread operator to convert the nodeList you get from getElementsByTagName to an array and then forEach() to loop through the array items. For each item, we add two event listeners. one for focus, and one for blur.
When focused, we add the attribute. When blurred we remove the attribute. I opted for set attribute and remove attribute, but you can also use dataset if you want.
To determine what i (the method) is, I used let and a ternary operator.
I'm still not sure why you want to override the method when a key is pressed on the keyboard so I left that. I can improve that if you let me know what the desired effect is.
let i = ("ontouchstart" in window) ? "touch" : "mouse";
document.addEventListener("keydown", () => {
i = "keyboard"
})
const links = [...document.getElementsByTagName("a")];
links.forEach(link => {
link.addEventListener("focus", () => {
link.setAttribute('data-focus-method', i);
});
link.addEventListener("blur", () => {
link.removeAttribute('data-focus-method');
})
})
My link 1
My link 2
My link 3
I got the solution adding:
var w;
for (w = 0; w < r.length; w++) {
r[w].addEventListener("focus", function() {
this.setAttribute("data-focus-method", i);
});
r[w].addEventListener("blur", function() {
this.removeAttribute("data-focus-method");
});
}
By the way, thanks for everyone who helped me!
I am very new to Javascript.
I am trying to write this baby jQuery plugin that I will use to make dropdown lists. What I am failing to achieve (beyond things that I do not notice) is to neatly exit or deactivate my active instance as I click on another instance. I tried to illustrate my problem in the following fiddle (keeping the structure I am using):
https://jsfiddle.net/andinse/m0kwfj9d/23/
What the Javascript looks like:
$(document).ready(function() {
$.fn.activator = function() {
var Activator = function(el) {
this.html = $('html');
this.el = el;
this.is_active = false;
this.initialize();
};
Activator.prototype.initialize = function() {
var self = this;
self.el.on('click', function(e) {
if (self.is_active === false) {
self.toggle('activate');
} else {
self.toggle('deactivate');
}
});
};
Activator.prototype.toggle = function(action) {
var self = this;
if (action === 'activate') {
console.log('activating ' + self.el[0].className);
self.is_active = true;
self.el.addClass('red');
self.html.on('click', function(e) {
if (e.target != self.el[0]) {
self.toggle('deactivate');
}
});
}
if (action === 'deactivate') {
console.log('deactivating ' + self.el[0].className);
self.is_active = false;
self.el.removeClass('red');
self.html.off('click');
}
};
if (typeof this !== 'undefined') {
var activator = new Activator(this);
}
return this;
};
$('.a').activator();
$('.b').activator();
$('.c').activator();
});
My idea was:
To watch for clicks on html as soon as the instance is active (thus ready to be deactivated). On click, to check if the event.target is the same as the active instance. If not, to deactivate this instance.
To stop watching for clicks as soon as the instance is inactive. So that we're not doing unnecessary work.
When it is set like this, it seems to work for only one cycle (click on A activates A then click on B activates B and deactivates A then click on C activates C but doesn't deactivate B).
If I get rid of the "self.html.off('click')" it seems to work kind of ok but if I look at the log I can see the "toggle" function is sometimes triggered multiple times per click. There must be a cleaner way.
Any piece of help greatly appreciated.
With your logic, when clicking any element you should deactivate any current activated element. Either do it globally:
$('.your_activation_class').removeClass('.your_activation_class');
or in some parent scope
$('some_parent_selector .your_activation_class').removeClass('.your_activation_class');
I've written a few events to handle opening and closing of a snap js drawer. This code below works, but I feel it could be written more efficiently. Any suggestions?
function openMobileMenu() {
event.preventDefault();
snapper.open('left');
$('#btn-menu').off('click', openMobileMenu);
$('#btn-menu').on('click', closeMobileMenu);
}
function closeMobileMenu() {
event.preventDefault();
snapper.close('left');
$('#btn-menu').on('click', openMobileMenu);
$('#btn-menu').off('click', closeMobileMenu);
}
$('#btn-menu').on('click', openMobileMenu);
Make your code modular and your concepts explicit.
You can start by creating a MobileMenu object which encapsulates the logic.
Note: The following code was not tested.
var MobileMenu = {
_snapper: null,
_$button: null,
_direction: 'left',
init: function (button, snapper, direction) {
this._$button = $(button);
this._snapper = snapper;
if (direction) this._direction = direction;
this._toggleSnapperVisibilityWhenButtonClicked();
},
_toggleSnapperVisibilityWhenbuttonClicked: function () {
this._$button.click($.proxy(this.toggle, this));
},
toggle: function () {
var snapperClosed = this._snapper.state().state == 'closed',
operation = snapperClosed? 'open' : 'closed';
this._snapper[operation](this._direction);
}
};
Then in your page you can just do the following to initialize your feature:
var mobileMenu = Object.create(MobileMenu).init('#btn-menu', snapper);
Modularizing your code will make it more maintainable and understandable in the long run, but also allow you to unit test it. You also gain a lot more flexibily because of the exposed API of your component which allows other code to interact with it.
E.g. you can now toggle the menu visibility with mobileMenu.toggle().
Use a variable to keep track of the state:
var menu_open = false;
$("#btn-menu").on('click', function(event) {
event.preventDefault();
if (menu_open) {
snapper.close('left');
} else {
snapper.open('left');
}
menu_open = !menu_open; // toggle variable
});
snap has a .state() method, which returns an object stuffed with properties, one of which is .state.
I think you want :
$('#btn-menu').on('click', function() {
if(snapper.state().state == "closed") {
snapper.open('left');
} else {
snapper.close('left');
}
});
Or, in one line :
$('#btn-menu').on('click', function() {
snapper[['close','open'][+(snapper.state().state == 'closed')]]('left');
});
Also, check How do I make a toggle button? in the documentation.
I am writing a piece of code that changes some lights on a screen from red to green randomly and waits for the user to hit the key that corresponds to the light lit.
When I run this code you are able to hit the a,d,j or l key and an alert will pop up. However, as soon as I click the start button no keys are recognised. And when the loop has finished the bind still seems to become disabled. I have tried moving the bind to other places but I have had no joy. Your help is much appreciated.
$( function() {
$('#start').bind('click', function() { main(); });
$(document).bind('keypress', function(e) { keyPress(e); } );
} );
function getRand(val) {
return Math.floor(Math.random()*val)+1;
}
function main() {
preD = new Date;
preDs = preD.getTime();
randTime=Math.floor(Math.random()*1001)+1500;
playSound();
flash();
}
function flash() {
zone = getZone();
setTimeout(function() {
$('#r'+zone).css("background-image", "url(images/rea_grn.jpg)");
setTimeout(function() {
$('#r'+zone).css("background-image", "url(images/rea_red.jpg)");
if(cond[1] < 8) {
main();
}
} , 200);
} , randTime);
}
function getZone() {
if(condition==1) {
zone = getRand(2);
if( test[1][zone] < 8 ) {
test[1][zone] += 1;
cond[1] += 1;
return zone;
} else {
getZone();
}
}
}
function keyPress(e) {
var evtobj=window.event? event : e //distinguish between IE's explicit event object (window.event) and Firefox's implicit.
var unicode=evtobj.charCode? evtobj.charCode : evtobj.keyCode
var actualkey=String.fromCharCode(unicode)
if (actualkey=="a" || actualkey=="d" || actualkey=="j" || actualkey=="l" ) {
dd = new Date;
reat = dd.getTime();
alert(1);
//keypressed[condition][zone]['k']=actualkey;
//keypressed[condition][zone]['t']=(reat-preDs);
}
}
The reason that this could be happening is, when you generate code dynamically or alter any existing code the bind needs to be done again, because the function to bind just runs once and only for the members already created. So when you create dynamically code, you are forced to run the binding function to recognize the new elements.
this ways is not very recommended, instead of this, you could bind a container like 'div' or something and inside of this validate which element is calling you. This will work because your container is created once and the binding is properly assigned and doesn't matter if the content of your container changes, the binding always work.
Regards
Using a jquery sound plugin was the answer.
Fixed it with this : plugins.jquery.com/project/sound_plugin
I'm using the CSS3 :target pseudo selector to create in-page navigation without reloading the page. This works really well!
But I have a problem, I need to reset the forms in a page when the page targetted, how can I know if an element is targetted with javascript? Like element.ontarget = function();
Or maybe something like element.ondisplaychange -> element.oncsschange?
BETTER UPDATE:
var hashcache = document.location.hash;
window.onhashchange = function() {
if(hashcache != document.location.hash) {
$(hashcache + ' form input').each(function() {
$(this).val('');
});
hashcache = document.location.hash;
}
}
UPDATE:
$('a[href^="#"]').each(function() {
this.onclick = function() {
href = $(this).attr('href');
if(href != document.location.hash) {
$(href + ' form input').each(function() {
$(this).val('');
});
}
}
});
If you're using JavaScript for the navigation, I'd suggest just adding the check to that. But I'm guessing from your question you're not, that you're instead using plain links with just anchors (e.g., <a href='#target1'>, <a href='#target2'>, ...).
A couple of options:
Use a Timer
In that case, basically what you want to do boils down to receiving an event when the anchor changes. As far as I know, and as far as the people answering this other question on StackOverflow in January knew, you can only do that with a timer. (Edit: But see ide's comment below, there's a new hashchange event we'll be able to use soon!) E.g.:
(function() {
var lastHash = window.location.hash;
setTimeout(function() {
var newHash = window.location.hash;
if (newHash !== lastHash) {
lastHash = newHash;
// Trigger your target change stuff
}
}, 250);
})();
That checks for changes every quarter second. That may not be enough for you, you could lower the 250, but beware running too much and slowing everything else down.
But as you say below, this is inefficient.
Hook the Link's click event
Since you're already using JavaScript on the page, I'd recommend using handlers on your links instead. If you add a class name or something to them (I bet they already have one; I'll us "navlink" below), this is easily set up:
var links, index, link;
links = document.getElementsByTagName('a');
for (index = 0; index < links.length; ++index) {
link = links.item(index);
if ((" " + link.className + " ").indexOf(" navlink ") >= 0) {
hookEvent(link, 'click', clickHandler);
}
}
function clickHandler() {
// `this` will reference the element that was clicked
}
// The 'hook' function:
var hookEvent = (function() {
var elm = document.createElement('a');
function hookEventViaAttach(element, event, handler) {
element.attachEvent("on" + event, handler);
}
function hookEventViaAddListener(element, event, handler) {
element.addEventListener(event, handler, false);
}
function hookEventDOM0(element, event, handler) {
element["on" + event.toLowerCase()] = handler;
}
if (elm.attachEvent) {
return hookEventViaAttach;
}
if (elm.addEventListener) {
return hookEventViaAddListener;
}
// I usually throw a failure here saying not supported, but if you want,
// you can use the DOM0-style stuff.
return hookEventDOM0;
})();
A lot of the complication of the above goes away if you use a library like jQuery, Prototype, YUI, Closure, or any of several others.
For instance, the jQuery version:
$("a.navlink").click(clickHandler);
function clickHandler() {
// `this` will reference the element that was clicked
}
The Prototype version:
$$("a.navlink").invoke('observe', 'click', clickHandler);
function clickHandler() {
// `this` will reference the element that was clicked
}
The onfocus property returns the onFocus event handler code on the current element.
event handling code = element.onfocus
The onblur property returns the onBlur event handler code, if any, that exists on the current element.
element.onblur = function;
Example: http://jsfiddle.net/g105b/cGHF7/
<html>
<head>
<title>onblur event example</title>
<script type="text/javascript">
var elem = null;
function initElement()
{
elem = document.getElementById("foo");
// NOTE: doEvent(); or doEvent(param); will NOT work here.
// Must be a reference to a function name, not a function call.
elem.onblur = doEvent;
};
function doEvent()
{
elem.value = 'Bye-Bye';
alert("onblur Event detected!")
}
</script>
<style type="text/css">
<!--
#foo {
border: solid blue 2px;
}
-->
</style>
</head>
<body onload="initElement()";>
<form>
<input type="text" id="foo" value="Hello!" />
</form>
<p>Click on the above element to give it focus, then click outside the
element.<br /> Reload the page from the NavBar.</p>
</body>
</html>
Maybe youcan just code like this
function hashChangeEvent(){
$(window.location.hash)//do something
}
window.onhashchange = hashChangeEvent;//when hash change
hashChangeEvent();//first load