Develop Reference

Hide Element when hover Element Javascript

I have a DIV that needs to be displayed/hide whenever i hover a menu item.
Here it is my website: Website
The Blug light section should be displayed only when I hover the Photo Booths menu on the header.
I have tried the following code on JSFiddle which it works but when i use it on my site it doesn't work
<script>
let test = document.getElementByClassName(".menu-item.menu-item-7912");
test.addEventListener("mouseover", function( event ) {
document.getElementById('test2').style.display = 'none';
});
test.addEventListener("mouseleave", function( event ) {
document.getElementById('mega-menu-customized').style.display = 'block';
});
</script>
I have tried using getElementByClassName but without success. Any ideas of how to make it work?

Are you getting DOM node in test variable, one problem I can see in your code is:
let test = document.getElementsByClassName(".menu-item.menu-item-7912");
Should be:
let test = document.getElementsByClassName("menu-item, menu-item-7912");
We do not use dot before class name and multiple classes can be separated by comma like:
let test = document.getElementsByClassName("class1, class2, class3");

Your issue is in the header element. On scroll, the style property of the document header is changing. Look:
sorry for the bad quality, upload size is maxed at 2MB
Without getting into too much detail, one thing that I see is that the height of the header is being reduced to only contain the main header. When the larger blue subheader is visible, part of that is because the style.height of the header is made to be much larger. Additionally, the first child of the header is a div with id 7905, and that seems to be what you need to target to modify the opacity of the larger blue header. You need to target that div:
const blueBannerContainer = document.getElementById('7905')
But your event handlers will also need to account for the height of the header element. display: block won't really help you here.

How can I change css for every DOM object in the page in SAPUI5

I have a things inspector and this things inspector has two titles. I wan to be able to change the css on this titles and make their font size a bit smaller( default fontSize is 16px and I want to drop it to 12px). I tried to get these titles class and use this method to change their size:
var element = document
.getElementsByClassName("sapUiUx3TVTitleSecond")[1];
element.style.fontSize = '12px';
var element = document
.getElementsByClassName("sapUiUx3TVTitleFirst")[1];
element.style.fontSize = '12px';
it does work and I can see the change but as soon as the page finishes loading ( page loading takes couple of second because it needs to read a json object) title sizes go back to its default.
I dont even know this is a right way to access DOM elements and change their CSS.
Please point me to the right direction of how to change DOM object css in SAPUI5 in general

You could create a new CSS file which you include in your index.html.
Just add the needed selectors with the modified attributes in this custom CSS:
.sapUiUx3TVTitleSecond, .sapUiUx3TVTitleFirst {
font-size : 12px;
}
Edit: if you need to change it programmatically, you could use the addStyleClass("yourStyle") method which is available to every UI element

Execute the script after dom gets completely loaded. Try like this
$("document").ready(function()
{
var element = document
.getElementsByClassName("sapUiUx3TVTitleSecond")[1];
element.style.fontSize = '12px';
var element = document
.getElementsByClassName("sapUiUx3TVTitleFirst")[1];
element.style.fontSize = '12px';
})

$("document").ready(function()
{
$(".sapUiUx3TVTitleSecond").css("font-size","12px");
})

How Can I Rewrite This More Efficiently

I have to believe that there's a better way to write the below code. Thanks in advance.
var hProtein = $('#protein-lbl');
var hCarb = $('#carb-lbl');
var hFat = $('#fat-lbl');
var hTotal = $('#totalCalories');
// Normal Calc vars
var nProtein = $('#protein-normal-lbl');
var nCarb = $('#carb-normal-lbl');
var nFat = $('#fat-normal-lbl');
var nTotal = $('#totalCalories-normal');
// Hide calculations until bodyweight is entered
hProtein.hide();
hCarb.hide();
hFat.hide();
hTotal.hide();
nProtein.hide();
nCarb.hide();
nFat.hide();
nTotal.hide();

Perhaps giving the HTML elements a class will work?
var $ele = $('.class-name');
$ele.hide();

The best solution is to have the default condition of the page specified in HTML/CSS, so it displays properly at first and you don't have to run a bunch of javascript just to set up the default condition.
So, if what you're trying to do is establish the default condition upon page load, change the display style of all these elements to style="display: none;" right in the HTML so they start out with the right state.
Or better yet, give them all a common class name and create a CSS style rule so they are all initially hidden. Doing this in the markup/CSS will prevent them showing and then hiding as your script runs - they will just start out with the right state.
CSS:
.initialHidden {
display: none;
}
HTML:
<div id="totalCalories-normal" class="initialHidden"></div>

add common class to element the hide it by this way
$('.common-class-name').hide()
OR
Put all elements in Single div wrap and hide it by that id

I would do this :
$([
'#protein-lbl',
'#carb-lbl',
'#fat-lbl',
'#totalCalories',
'#protein-normal-lbl',
'#carb-normal-lbl',
'#fat-normal-lbl',
'#totalCalories-normal'
].join()).hide();

Why not wrap the labels in a fieldset and hide the fieldset

How to dynamically set and modify CSS in JavaScript?

I have some JavaScript code that creates some div elements and it sets their CSS properties.
Because I would like to decouple CSS logic from my JavaScript code and because CSS is easier to read in its own .css file, I would like to set the CSS className of my element and then dynamically inject some values into the defined CSS property.
Here is what I would like to do :
style.css:
.myClass {
width: $insertedFromJS
}
script.js:
var myElement = document.createElement("div");
myElement.className = "myClass";
I want to do something like this but at that point myElement.style.width is empty
myElement.style.width.replaceAll("$insertedFromJS", "400px");
I think my problem here is that after the call to myElement.className = "myClass", the CSS is not yet applied.

If I understand your question properly, it sounds like you're trying to set placeholder text in your css file, and then use javascript to parse out the text with the css value you want to set for that class. You can't do that in the way you're trying to do it. In order to do that, you'd have to grab the content of the CSS file out of the dom, manipulate the text, and then save it back to the DOM. But that's a really overly-complicated way to go about doing something that...
myElement.style.width = "400px";
...can do for you in a couple of seconds. I know it doesn't really address the issue of decoupling css from js, but there's not really a whole lot you can do about that. You're trying to set css dynamically, after all.
Depending on what you're trying to accomplish, you might want to try defining multiple classes and just changing the className property in your js.

Setting the style, might be accomplished defining the inner-page style declaration.
Here is what i mean
var style = document.createElement('style');
style.type = 'text/css';
style.cssText = '.cssClass { color: #F00; }';
document.getElementsByTagName('head')[0].appendChild(style);
document.getElementById('someElementId').className = 'cssClass';
However the part of modifying it can be a lot of tricky than you think. Some regex solutions might do a good job. But here is another way, I found.
if (!document.styleSheets) return;
var csses = new Array();
if (document.styleSheets[0].cssRules) // Standards Compliant {
csses = document.styleSheets[0].cssRules;
}
else {
csses = document.styleSheets[0].rules; // IE
}
for (i=0;i<csses.length;i++) {
if ((csses[i].selectorText.toLowerCase()=='.cssClass') || (thecss[i].selectorText.toLowerCase()=='.borders'))
{
thecss[i].style.cssText="color:#000";
}
}

could you use jQuery on this? You could use
$(".class").css("property", val); /* or use the .width property */

There is a jQuery plugin called jQuery Rule,
http://flesler.blogspot.com/2007/11/jqueryrule.html
I tried it to dynamically set some div sizes of a board game. It works in FireFox, not in Chrome. I didn't try IE9.

How can I undo the setting of element.style properties?

I have an element in my document that has a background color and image set through a regular CSS rule.
When a certain event happens, I want to animate that item, highlighting it (I'm using Scriptaculous, but this question applies to any framework that'll do the same).
new Effect.Highlight(elHighlight, { startcolor: '#ffff99', endcolor: '#ffffff', afterFinish: fnEndOfFadeOut });
The problem i'm facing is that after the animation is done, the element is left with the following style (according to FireBug):
element.style {
background-color:transparent;
background-image:none;
}
Which overrides the CSS rule, since it's set at the element level, so I'm losing the background that the item used to have...
What I'm trying to do is, in the callback function I'm running after the animation is done, set the style properties to a value that'll make them "go away".
var fnEndOfFadeOut = function() {
elHighlight.style.backgroundColor = "xxxxx";
elHighlight.style.backgroundImage = "xxxxx";
}
What I'm trying to figure out is what to put in "xxxx" (or how to do the same thing in a different way).
I tried 'auto', 'inherit', and '' (blank string), and neither worked (I didn't really expect them to work, but I'm clueless here).
I also tried elHighlight.style = ""; which, expectably, threw an exception.
What can I do to overcome this?
I know I can put a span inside the element that I'm highlighting and highlight that span instead, but I'm hoping I'll be able to avoid the extra useless markup.

Chances are you're not setting the style on the correct element. It's probably being set somewhere up the line in a parent node.
elHighlight.style.backgroundColor = "";
elHighlight.style.backgroundImage = "";
You can also remove all the default styling by calling:
elHighlight.style.cssText = "";
In any case, you'll still have to do this on the specific element that is setting these properties, which means you may need to do a recursion on parentNode until you find it.

Try
elHighlight.style.removeProperty('background-color')
elHighlight.style.removeProperty('background-image')

have you tried elHightlight.style.background = "";?
I have a highlighter code on my site and this works
function highlight(id) {
var elements = getElementsByClass("softwareItem");
for (var ix in elements){
elements[ix].style.background = ""; //This clears any previous highlight
}
document.getElementById(id).style.background = "#E7F3FA";
}

An HTML element can have multiple CSS classes. Put your highlight information inside a CSS class. Add this class to your element to highlight it. Remove the class to undo the effect.