Develop Reference

Jquery show or hide children link if it is available

I have a question on Jquery. If I click on Link1, which does not have any ul.children and the class current_page_item will be added(not shown in this code as it will be added automatically by Wordpress), then ul.children in Link2 should be hidden.
If i click on Link 2, which will have both class page_item_has_children current_page_item, in this case ul.children should be shown. I have tried my code bellow, which is i know it is absolutely wrong. Please give me your advices. Many thanks.
if($(.navigation).hasClass(page_item_has_children)){
(.navigation .page_item_has_children .children).hide();
}else if( $(.navigation).hasClass(page_item_has_children) && $(.navigation).hasClass(current_page_item)){
(.navigation .page_item_has_children .children).show();
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<ul class="navigation">
<li>Link1</li>
<li class="page_item_has_children current_page_item">Link2
<ul class="children">
<li class="page_item">Link3</li>
<li class="page_item ">Link4</li>
</ul>
</li>
</ul>

This solution is a bit more towards your scenario (edited based on comment):
$(".navigation li").on("click", function() {
if ($(this).hasClass("page_item_has_children") && $(this).hasClass("current_page_item")) {
$(".navigation .children").show();
} else {
$(".navigation .children").hide();
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<ul class="navigation">
<li>Link1
</li>
<li class="page_item_has_children current_page_item links">Link2
<ul class="children">
<li class="page_item">Link3
</li>
<li class="page_item ">Link4
</li>
</ul>
</li>
</ul>

How about simply hiding all nested UL elements, then simply showing the children of the clicked one?
$(".navigation li").each(function() {
// When we first load, hide all nested menus.
$(this).children("ul").hide();
if (localStorage.menuNumber) {
$(".navigation li").eq(localStorage.menuNumber).children().show();
}
})
.on("click", function() {
// When any top-level ul is clicked, hide the
// nested menus then show the current one.
$(this).parent().children().find("ul").hide();
$(this).children().show();
// We also want to persist this selection,
// should the user refresh...
localStorage.menuNumber = $(this).index;
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<ul class="navigation">
<li>Link1
</li>
<li class="page_item_has_children current_page_item">Link2
<ul class="children">
<li class="page_item">Link3
</li>
<li class="page_item ">Link4
</li>
</ul>
</li>
</ul>
Edited it so that when it initially loads, all nested uls are hidden. Hope this helps! And edited again, to store the clicked menu in local storage. Sadly, for security reasons, this won't work here. See it as a fiddle: https://jsfiddle.net/snowMonkey/fnuvvLwb/

removing a class x number in a list

Trying to figure out a way to remove classes in sets of 4 within a list item.
So let's say I have an unorder list with 50 list items with 40 of the items having a class of 'hide'. I have a button that handles a click event to remove 4 of the li's hide class.
HTML
<ul>
<li>foo</li>
<li>foo</li>
<li>foo</li>
<li>foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
<li class="hide">foo</li>
</ul>
<button>Click me to see the next 4 items</button>
JavaScript
$('button').click(function () {
$('li.hide').removeClass('hide');
})

Try like this
$('button').on('click',function() {
$('li.hide').each(function(i) {
if (i == 4)
return false;
$(this).removeClass('hide');
});
});

use the :lt() selector:
$('button').click(function() {
$('li.hide:lt(4)').removeClass('hide');
});
Fiddle: http://jsfiddle.net/mrub5b0z/

How to get a previous DIV with jQuery

I want to animate an element (.item-i) after I click on another element(.item-1) which is following below. Now I don't know, how to get to this element.
I want only the exact above element animated, not both above, only the first element above.
I made an easy show up in http://jsfiddle.net/Eef4v/1/. The YellowBG is the "animation".
Here is my JS code:
$('.item-1').click(function() {
$(this).closest('.item-i').css( "background", "yellow" );
});
And my HTML Markup:
<ul id="one" class="level-1">
<li class="item-i">I</li>
<li class="item-ii">II
<ul class="level-2">
<li class="item-a">A</li>
<li class="item-b">B
<ul class="level-3">
<li class="item-1">1</li>
<li class="item-2">2</li>
<li class="item-3">3</li>
</ul>
</li>
<li class="item-c">C</li>
</ul>
</li>
<li class="item-iii">III</li>
</ul>
<ul id="Ul1" class="level-1">
<li class="item-i">I</li>
<li class="item-ii">II
<ul class="level-2">
<li class="item-a">A</li>
<li class="item-b">B
<ul class="level-3">
<li class="item-1">1</li>
<li class="item-2">2</li>
<li class="item-3">3</li>
</ul>
</li>
<li class="item-c">C</li>
</ul>
</li>
<li class="item-iii">III</li>
</ul>

Use:
$(this).closest('.item-ii').prev().css( "background", "yellow" );
Working Demo
For Toggling background color:
$(this).closest('.item-ii').prev().toggleClass("highlight");
CSS:
.highlight {background: yellow;}
Demo with ToggleClass

Two ways to get .item-i to highlight.
$(this).parents('.level-1').find('.item-i').css( "background", "yellow" );
but if you have multiple .item-i classes under your .level-1 then they would all turn yellow.
Working Demo
You could also write a find algorithm that goes through each parent of .item-1 and finds the closest item-i
$('.item-1').click(function () {
$(this).parents().each(function(index,elem){
var query = $(elem).find('.item-i');
if(query.length > 0)
{
query.first().css("background-color", "yellow");
return false;
}
});
});
Working Algorithm demo

JQuery - Make .slideToggle specific to each list

I have a .slideToggle making a list dropdown, but unfortunately it makes all lists dropdown, I need to make it only dropdown the list below the a that I'm clicking on. Sure this is a simple issue, still pretty new to jquery.
Jsfiddle: http://jsfiddle.net/darcyvoutt/shErA/

The following finds the next ul element and runs slideToggle() on it.
$(document).ready(function () {
$('.nav-filters-list-item a').click(function () {
$(this).next('ul').slideToggle(70);
});
});
See this jsFiddle

Try adding an id for each dropdown like this:
<ul class="nav-filters-list">
<li class="nav-filters-list-item" id="genre">Genre
<ul>
<li>Sub-Home
</li>
<li>Sub-Home
</li>
<li>Sub-Home
</li>
</ul>
</li>
<li class="nav-filters-list-item" id="tags">Tags
<ul>
<li>Sub-Home
</li>
<li>Sub-Home
</li>
<li>Sub-Home
</li>
</ul>
</li>
<li class="nav-filters-list-item">Date
</li>
<li class="nav-filters-list-item">Order
</li>
</ul>
Javascript:
$(document).ready(function () {
$('#genre a').click(function () {
$('#genre ul').slideToggle(70);
});
$('#tags a').click(function () {
$('#tags ul').slideToggle(70);
});
});

open the first section when page loads

HTML:
<li class="page_item ">
A
<ul class="children">
<li class="page_item">1</li>
<li class="page_item">2</li>
</ul>
</li>
<li class="page_item ">
B
<ul class="children">
<li class="page_item">1</li>
<li class="page_item">2</li>
<li class="page_item">3</li>
<li class="page_item">4</li>
</ul>
</li>
<li class="page_item ">
C
<ul class="children">
<li class="page_item">1</li>
<li class="page_item">2</li>
<li class="page_item">3</li>
<li class="page_item">4</li>
</ul>
</li>
JS:
$('.page_item').click(function() {
var that = this;
$('.page_item').each(function() {
if (that == this) return true; //continue
$('.children:not(:hidden)', this).slideToggle();
});
$('ul.children', this).slideToggle();
});
Online demo: http://jsfiddle.net/kHLuR/1/
How can I make the first section li opened by default?

Variant #1 Pure CSS solution:
.page_item:first-child .children {
display: block;
}
Demo: http://jsfiddle.net/dfsq/kHLuR/7/
Note: :first-child works in IE8+. If you need to support older version you can give another class to your first li, e.g: <li class="page_item page_item-first"> http://jsfiddle.net/dfsq/kHLuR/9/
Variant #2. Trigger click event on the first .page_item:
$('.page_item').click(function () {
// ...
})
.filter(':first').click();
Demo: http://jsfiddle.net/dfsq/kHLuR/8/

Add this code to simulate a click event when the page is loaded: LIVE DEMO
$(document).ready(function () {
$('a').eq(0).trigger('click');
});

You can use jQuery's .ready() to execute code immediately after the page loads.
Take a look at http://api.jquery.com/ready/