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How to change CSS over selected element only using $(this)

I'm trying to make it where when the user .mouseover() the .featured_products the .featured_products, and the .button will apply the CSS affect to the selected container. The problem i'm encountering is it changes the .css of both the .feature_products containers. I'd like it to only change the one that's being .mouseover(). I tried using $(this) but i'm not understanding it correctly.
$(".featured_products").mouseover(function(){
$(".fp_button").css("background-color", "#00addc");
$(".fp_button").css("color", "#FFFFFF");
$(this).addClass("fp_hover");
});
$(".featured_products").mouseleave(function(){
$(".fp_button").css("background-color", "white");
$(".fp_button").css("color", "#000000")
$(".featured_products").removeClass("fp_hover");
});
Here is my Demo

You can use the second parameter in the selector to denote a parent, like:
$(".fp_button", this).css("background-color", "#00addc");
See it here: http://jsfiddle.net/4417zugn/31/
You can also do something like:
$(this).find(".fp_button")...
etc. There are many ways.
One thing I'd suggest is to change the class name instead of modifying individual CSS rules, like this: http://jsfiddle.net/4417zugn/33/
Last thing, this is all possible using only CSS, like this: http://jsfiddle.net/4417zugn/35/

There's no need to use jQuery to alter the CSS you can do that in the CSS itself using the :hover selector. You can then use jQuery to toggle the 'fp_hover' class.
$('.featured_products').hover(function(){
$(this).toggleClass('fp_hover')
})
https://jsfiddle.net/Lozgnz84/

$(".fp_button") is common for both the divs; so
instead of writing:
$(".fp_button").css("background-color", "white");
Write:
$(this).find('.fp_button').css("color", "#FFFFFF");
Hence, your code becomes
$(".featured_products").mouseover(function(){
$this = $(this);
$this.find('.fp_button').css({"background-color":"#00addc", "color":"#FFFFFF"});
$this.addClass("fp_hover");
});
$(".featured_products").mouseleave(function(){
$this.find('.fp_button').css({"background-color":"white", "color":"#000000"});
$this.removeClass("fp_hover");
});
demo here: http://jsfiddle.net/znnamrwn/

What you've described can be done without jQuery. If however you would like to use jQuery you could simply toggle a class on the product element.
$('.featured_products').on({
mouseenter: function() {
$(this).toggleClass('fp_hover');
},
mouseleave: function() {
$(this).toggleClass('fp_hover');
}
}, '.featured_product');
http://jsfiddle.net/bradlilley/uwxsr4hu
You can also do the above without jQuery by simple adding the following hover state in your css.
.featured_product:hover .fp_button {
background: #f00;
color: #000;
}
https://jsfiddle.net/bradlilley/9mwxo9o2/6/
Edit: You should also avoid using mouseover and use mouseenter instead.
Jquery mouseenter() vs mouseover()

jQuery selector precedence when using pattern matching

I am creating a form that implements a bunch of similar elements. They are custom select boxes, created out of <ul>s.
Some of these elements are slightly different in the way I want the mousedown event to be handled though.
The way I have it set up currently is that, by appending _custom_select to the end of an elements class name, it will be treated as one of these special elements as far as CSS is concerned.
However, when the string selections is found inside a class name (that will coincidentally also end with _custom_select in order to apply the proper styling) I want to use a different mousedown event handler.
This is the relevant section of my event listener set up:
$('[class$="_custom_select"] li').mousedown(function(event){
var opt= event.target;
if(opt.className!='li_disabled' && event.which==1)
{
if(opt.className=='li_unselected'){
opt.className= 'li_selected';
}
else{
opt.className= 'li_unselected';
}
update_selections(opt.parentElement);
}
});
$('[class*="selections"]').mousedown(function(event){
var opt=event.target;
if(event.which==1){
if(opt.className=='li_unselected'){
opt.className= 'li_selected_2';
}
else{
opt.className= 'li_unselected';
}
}
});
This code works, but notice how, in the second binding, I had to bind the event listener to the ul that holds the li that is actually being clicked.(The ul is the element whose class name matches the pattern) In the first one however, I can bind the event listener directly to the li elements contained within the ul.
If I change the second jQuery selector to $('[class*="selections"] li') the event listener is never bound to the corresponding lis.
What is causing this behavior?
I am aware that I can just check event.target.tagName to ensure the event is bubbling up from an <li>, but that is not what the question is about.
I originally thought it had something to do with precedence and that the listeners weren't being bound because the lis that would have matched the second selector already matched against the first selector.
However, after implementing logging and looking at the DOM I have determined that when I change the second selector to: $('[class*="selections"] li') neither event listener is bound to the lis that match the second selector.
Here is a link to a JS fiddle of the 'working version'. If you add ' li' to the second selector and then try to click the <li>s in the box to the right, you will see that they no longer become green.
jsFiddle
https://jsfiddle.net/6sg6z33u/4/

Okay, thanks for posting the jsFiddle. This is an easy fix!
The elements in your second li are being added dynamically. When you bind to elements using the shortcut methods like .click() it only binds to the elements on the page when it initially bound
The fix: use the .on() method, which is the preferred method per jQuery foundation. This method allows for live binding meaning it will pick up on dynamic elements.
$('[class*="selections"]').on( 'mousedown', 'li', function(event) {
var opt = event.target;
if (event.which == 1) {
if (opt.className == 'li_unselected') {
opt.className = 'li_selected_2';
} else {
opt.className = 'li_unselected';
}
}
});

How to use js to query shadow dom element in Polymer?

I know how to query shadow dom element in <style> tag,but i want to use data-bind dynamically change the style,data-bind can not be applied in <style> in Polymer,so i should make it happen in js.For example,i use core-scroll-header-panel component, i can query its background style using:
<style>
core-scroll-header-panel::shadow #headerBg {
background: #5cebca;
}
</style>
but how can implement it in js?

Here's the way to select your element:
var shadow = document.querySelector('core-scroll-header-panel').shadowRoot;
var header = shadow.querySelector('#headerBg');
Note that it will return one single element. If you need to loop over multiple element you may use querySelectorAll as you probably know.
You can then change your background color as normal:
header.style.backgroundColor = "#5cebca";
However, changing a color in directly in JavaScript is not adviced and you should use CSS for that.
header.className = "my_css_class";
Note that it will return one single element. If you need to loop over multiple element you may use querySelectorAll as you probably know.

I have tried it out :
document.querySelector('core-scroll-header-panel::shadow #headerBg');
and is there any else solutions?

Hover all element in html

Is there any way to add hover on all elements in html (div,p,span,a...) I'm trying like this:
$("*").hover(
function () {
$(this).addClass('hover'); ;
},
function () {
$(this).removeClass('hover');
}
);
and CSS
#hover {
background-color:#CC0000;
}
but somewhere there is an error???

You should be using a . rather than a # to denote a class selector.
.hover {
background-color:#CC0000;
}
Also, note that using * as a jQuery selector will select everything, including the body element etc. I'm not sure from the context of the question whether this is what you're after or not.
Furthermore, it would be easier to just use the CSS pseudo-class :hover to apply a style to a hovered element. Here's a reference for how to use it: http://reference.sitepoint.com/css/pseudoclass-hover

You adding class "hover", but using CSS # selector for ids, use .hover instead of #hover

jlis solution will work, but there is a better way:
Use the css pseudo class ":hover" instead:
*:hover {
background-color: #CC0000;
}
should work with most common and actual browsers.
(IE 6 is not an actual or common browser!)

Change CSS rule in class using JQuery

I have a class in CSS
.Foo
{
width:20px;
}
Using Jquery I would like to do something similar to this on an event:
$(".Foo").css("width", "40px");
This doesn't work. Is this the wrong approach? Should I use addClass() and removeClass()?
EDIT: I figured out my problem. This command does in fact work. In my particular application I hadn't created the elements using the class before I used the command, so when they were created nothing was changed.
Basically this command doesn't change the CSS style rule, just the elements using the class.

You can change a CSS style rule. You need to look at:
document.styleSheets collection
styleSheet.cssRules property (or styleSheet.rules for IE7 and IE8)
rule.selectorText property
rule.style property
For example:
var ss = document.styleSheets[0];
var rules = ss.cssRules || ss.rules;
var fooRule = null;
for (var i = 0; i < rules.length; i++)
{
var rule = rules[i];
if (/(^|,) *\.Foo *(,|$)/.test(rule.selectorText))
{
fooRule = rule;
break;
}
}
fooRule.style.width = "40px";
Working demo: jsfiddle.net/kdp5V

you could add the styling manually to the header with jquery:
$('head').append('<style id="addedCSS" type="text/css">.Foo {width:40px;}</style>');
then change it on an event like e.g. so:
$(window).resize(function(){
$('#addedCSS').text('.Foo {width:80px;}');
});

jQuery.css will find all existing elements on the page that have the Foo class, and then set their inline style width to 40px.
In other words, this doesn't create or change a css rule -- if you dynamically add an element with the Foo class, it would still have a width of 20px, because its inline style hasn't been set to override the default CSS rule.
Instead, you should use addClass and removeClass and control the styles in your static CSS.

Yes, you should use addClass and removeClass to change the styling. In your css, define a couple of different classes and switch between them.

You should be selecting an element with jQuery. You're aware that you aren't selecting the CSS class itself, correct?
Once you have an element with class="Foo", you can select it as you have, and either set css properties manually like you're trying to do, or you can use add class like so:
$(".Foo").addClass('Foo');
Granted of course, since you're selecting the same class that you're adding, it doesn't really make sense.

I got thsi example in CSS api help in JQuery API.
this worked for me : http://jsfiddle.net/LHwL2/
for complete help read the css api at http://api.jquery.com/css/

Try using multiple styles
.FooSmall
{
width:20px;
}
.FooBig
{
width:40px;
}
$('#theTarget').removeClass('FooSmall').addClass('FooBig');

This may work for you.
$(".Foo").css("width", "40px");