Develop Reference

Reference child element in javascript

I am using the following piece of code in order to add a class to an li item.
JavaScript
$(document).on('click', '.sidenav .page_item_has_children', function({
$(this).addClass('side_open').siblings.removeClass('side_open')
})
As you can see It refers to the element that is clicked, in this instance an li. I need to apply this to the li's child element which is a ul so that the dropdown can appear. I assume I basically need something along the lines of the following however I can not work it out.
$(document).on('click', '.sidenav .page_item_has_children', function({
$(child).addClass('side_open').siblings.removeClass('side_open')
})
If anyone has any ideas on how this can be done that would be great!
Thanks - Scott

Using jQuery you could try jQuery(this).find('ul') or jQuery(this).children('ul');
See also: How to get the children of the $(this) selector?
Use $(this).find('ul'); to return all ul that are descendants of the li u referenced or $(this).children('ul') to find only 1st-level descendants.

How can I change an attribute value for all list items?

I have a simple structure like:
HTML
<ul id="costsDropdown">
<li data-position="bla bla"></li>
</ul>
and I want to change each "data-position" attribute of my list Elements.
My first Jquery Shot was this here:
$("#costsDropdown ul").each(function() {
$("li").attr("data-position", "TEST-VALUE123");
});
but it doesnt work, I think my selector are wrong...
could anyone give me a hint please?
Thanks for any help!
Greetz

Your selectors are a bit off
$("#costsDropdown ul").each
That is trying to select the child ul of the container #costsDropdown (which is the ID of the ul) - what you want is:
$("#costsDropdown li").each(function() {
$(this).attr("data-position", "TEST-VALUE123");
});
ID's are unique - no need to double up the selector with an ID and the type of element it is.
Note that I used $(this), not $("li"), inside the each callback. $("li") selects all li elements, anywhere on the page; we just want a jQuery wrapper for the one specific one we're handling inside the each.
In fact, the each is completely unnecessary because of the set-based nature of jQuery; if you use the .attr setter, it sets the attribute on all elements in the set:
$("#costsDropdown li").attr("data-position", "TEST-VALUE123");
That will set the value on all of the li elements inside #costsDropdown.
If you need to set separate individual values on the individual li elements, you still don't need each (though it's fine if you want to use it); you can use the version of attr that accepts a callback that it uses to find out what value to set:
$("#costsDropdown li").attr("data-position", function(index) {
return "Test value " + index;
});
That will set "Test value 0" on the first li, "Test value 1" on the second, etc. And like the each example above, if you need to, you can use this within the callback to refer to the li for that call (possibly using $(this) to wrap it if you need a jQuery wrapper).

$("#costsDropdown ul") matches no elements, it has to be $("#costsDropdown") (#costsDropdown is the ul).
And even that is unnecessary. Go
$("li[data-position]").attr("data-position", "TEST-VALUE123");
instead.

Cannot select all elements except one

I am trying to select all the elements of a page except one, inside a function:
$('#sidebutton').click(function () {
if (!$('.sidemenu').hasClass("current")) {
prevScrolPos = $(window).scrollTop();
scrollTo = 0;
} else {
scrollTo = prevScrolPos;
}
$('.hidelem').toggleClass("hidden");
$('.sidemenu').toggleClass("current");
$('html,body').scrollTop(scrollTo);
});
It works when I use a simple class selector (.hidelem), but doesn't when I use something a bit more complicated (for example, $("*:not(.sidemenu)").toggleClass("hidden"); or $("*").not(".sidemenu").toggleClass("hidden");); these just lead to a blank window.
Could you tell me what I'm missing here?
JSFiddle: https://jsfiddle.net/et978wjw/5/ (full functionality is missing but I hope you get the idea)

The problem is that you may be skipping .sideMenu with $("body *:not(.sidemenu)"), but you are not skipping its parent DIV. If you hide an ancestor, you hide all its descendants too. You also do not skip any descendants, so the children of .sidemenu are also hidden
So you need to exclude anything that is an ancestor of .sidemenu with :not:(has()), then exclude the sidemenu itself, then exclude any children of sidemenu:
$("#container :not(:has(.sidemenu)):not(.sidemenu):not('.sidemenu *')").toggleClass("hidden");
JSFiddle: https://jsfiddle.net/TrueBlueAussie/et978wjw/8/
You really should direct the hide/show at something more specific though. Perhaps a wrapper div around everything you want hidden? I added one for the demo.
Now having said all that, your selection process is quite complicated. You would be better off simply adding a class to all the things you want to toggle instead and just toggle those (you already have nodisplay on the divs, so I used that for now).
e.g. just this:
$(".nodisplay").toggleClass("hidden");
JSFiddle: https://jsfiddle.net/TrueBlueAussie/et978wjw/9/

Remove class from element and add to next element

I have a list of links, one has the class active.
On my next button click id like to remove the class from the current element and add it to the next only I cant seem to get it to add?
Ive made a fiddle to hopefully explain my problem, any help would be great, thanks
http://jsfiddle.net/h6D4k/
$('.next').click(function(){
$('ul.pagination').find('a.active').removeClass('active');
$('ul.pagination').find('a.active').next('a').addClass('active');
return false;
});

One of the jQuery most usable conveniencies is that its methods are (usually) chainable - in other words, they return the very object they are called from. So you can simply write this:
$('ul.pagination').find('a.active').removeClass('active').closest('li')
.next('li').find('a').addClass('active');
... as it's <li> elements that should be 'nexted', not <a> ones. But in fact, you shouldn't probably discard 'active' altogether if it's the last element in question:
var $a = $('ul.pagination').find('a.active'),
$li = $a.closest('li'),
$nextLi = $li.next('li');
if ($nextLi.length) {
$a.removeClass('active');
$nextLi.find('a').addClass('active');
}

This is actually what you want based on your html structure in you fiddle. http://jsfiddle.net/h6D4k/1/
$('ul.pagination').find('a.active').removeClass('active').parent()
.next().find('a').addClass('active');

Because once you've done this...
$('ul.pagination').find('a.active').removeClass('active');
There is no more a.active - the active classname has been removed from that element. So repeating the same selector...
$('ul.pagination').find('a.active')//...
... will select nothing.
Chain it all together instead.
$('ul.pagination').find('a.active').removeClass('active').next('a').addClass('active');
You have a second problem. According to the jQuery API for next(), it will:
Get the immediately following sibling of each element in the set of matched elements. If a selector is provided, it retrieves the next sibling only if it matches that selector.
You're not trying to get the following sibling:
<ul class="pagination">
<li><a class="one active" href="#">X</a></li>
<li><a class="two" href="#">X</a></li>
<li><a class="three" href="#">X</a></li>
</ul>
Next
Prev
You're trying to get the next <a> in the whole document. That's more challenging - and I'm not sure how to do it.

I would write it this way, preventing the action from doing anything on the last li as well.
http://jsfiddle.net/h6D4k/6/
$('.next').click(function(e){
e.preventDefault();
if ($("ul.pagination a.active").parent().is(":last-child")) return;
$('ul.pagination a.active').removeClass('active').parent().next().find("a").addClass('active');
});

You have two errors in your code:
Once removed, the active class can't be found anymore
your a tags are nested in li tags so next() doesn't work as you expect
To simplify things, you could attach the active class to the li tags.
Live demo: http://jsfiddle.net/h6D4k/7/
Code:
$('.next').click(function(){
$('ul.pagination').find('li.active').removeClass('active')
.next().addClass('active');
return false;
});

Selecting all but the first child of parent with an ID and then applying action

I want to select all the child elements of a parent element (except the first) with jQuery and I have the below..
$("li:not(:first-child)");
But I'm not sure how I can apply it to just the certain parent ID, would something like this work?
$('#myID').("li:not(:first-child)");
If so, I then want to add an element before the respective <li> tag. Would I then be able to do this with?
$('#myID').("li:not(:first-child)").before('<li>Test</li>');
I'm guessing something above is wrong as it isn't working.

Close, just pass in the selector context:
$("li:not(:first-child)", "#myID")
http://api.jquery.com/jQuery/
jQuery( selector [, context] )
selector: A string containing a selector expression
context: A DOM Element, Document, or jQuery to use as context
EDIT:
My initial answer assumed that you have no more li within the child's li. if you strictly only wants to select the children, use >:
$("#myID > li:not(:first-child)")

There's different solutions:
$("li:not(:first-child)", "#myID"); // see #SiGanteng answer
$("#myID li:not(:first-child)");
$("#myID").find("li:not(:first-child)");

Simple: using the :gt() help selector:
Just do it like: demo fiddle
$("#myID li:gt(0)").before('<li>Test</li>');
If you are concerned about speed :) :
$("#myID").find("li:gt(0)").before('<li>Test</li>');
or like: demo fiddle
$("#myID li:not(:first-child)").before('<li>Test</li>');

Assuming #myID is a ul or ol element, another possible way to get all children but the first is
$('#myID').children().slice(1)