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NO error display but cant slideUp();

I have this slide up and slide down. I can slide down the child on click but cant slide up when click again.
JavaScript
jQuery("#all li").on("click", function(e) {
e.preventDefault();
var parent = jQuery(this);
var father = parent.data("clicked", true);
var child = parent.find("ul");
var x = child.on(":visible");
if (parent.is(":visible")) {
child.slideDown("fast");
} else {
child.slideUp("fast");
}
});
HTML
<nav>
<ul id="all">
<li>Link 1</li>
<li>Link 2
<ul>
<li>Sub-Link 1</li>
<li>Sub-Link 2</li>
<li>Sub-Link 3</li>
</ul>
</li>
<li>Link 3
<ul>
<li>Sub-Link 1</li>
<li>Sub-Link 2</li>
<li>Sub-Link 3</li>
<li>Sub-Link 4</li>
</ul>
</li>
<li>Link 4</li>
<li>Link 5</li>
<li>Link 6</li>
</ul>
</nav>

It seems to me, based on your posted script and markup, that the parent is always visible. This means the if statement has essentially no effect. Altering it to check if the child is visible may help:
$('#all li').on('click', function() {
var parent = $(this);
var child = parent.find('ul');
if(child.is(':visible')){
$(child).slideUp('fast');
} else {
$(child).slideDown('fast');
}
});
Fiddle Demo

To achieve your expected result, use slideToggle()
JS:
jQuery("#all li").on("click", function(e) {
e.preventDefault();
var parent = jQuery(this);
var father = parent.data("clicked", true);
var child = parent.find("ul");
var x = child.on("visible");
if (parent.is("visible")) {
child.slideDown("fast");
} else {
child.slideToggle("fast");
}
});
http://codepen.io/nagasai/pen/jAkjBd

Find specific string in a div and delete its html element

is there a way using javascript to find a specific string and delete its' html element.
For example, I have this following html code:
<div class="summary">
List of texts:
<ul>
<li>Text 0</li>
<li>Text 1</li>
<li>Text 2</li>
<li>Text 3</li>
<li>Text 4</li>
<li>Text 5</li>
</ul>
</div>
and I want to hide "Text 2", first I want to find this string and then hide it.
what I've tried is using html().replace but it hides only the text not the element.
JSFiddle

In jQuery there is :contains
$('.summary li:contains(Text 2)').hide();
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="summary">
List of texts:
<ul>
<li>Text 0</li>
<li>Text 1</li>
<li>Text 2</li>
<li>Text 3</li>
<li>Text 4</li>
<li>Text 5</li>
</ul>
</div>

Your fiddle is pretty close. Here's an updated version removing the element from the DOM.
$('.summary li').each(function() {
var $this = $(this);
if ($this.text() === 'Text 2') {
$this.remove();
}
});
http://jsfiddle.net/sLa3dkdd/3/

Iterrate over li elements, check if the text content is the searched value, then hide or remove the element.
$(function() {
$('.summary li').each(function() {
var $this = $(this);
if($this.text() === 'Text 2'){$this.hide();}
});
});

using JQuery you can do it like that :
$('.summary ul').children().each(function () {
if($(this).text() == searchedValue) {
$(this).hide();
}
})

Select jquery elements except specific children

This is a simple question, but, I haven't found a clear answer in any of the question that I found. I modified a JSFiddle for my specific question.
I got this tiny code:
<ul>
<li id='one'>Element 1</li>
<li id='two'>Element 2</li>
<li id='three'>Element 3</li>
<li id='four'>Element 4</li>
<li id='five'>Element 5</li>
</ul>
and this script should return the ul element excepting the first li:
$(function(){
$("ul").not($('#one'))
});
Instead, it removes every li. What have I done wrong?
EDIT: In others words, I would like a selector which selects this, without removing the actual element (= inside a variable)
<ul>
<li id='two'>Element 2</li>
<li id='three'>Element 3</li>
<li id='four'>Element 4</li>
<li id='five'>Element 5</li>
</ul>
FIDDLE: http://jsfiddle.net/LVUMs/13/

Use
$("ul li").not($('#one')).remove();
DEMO
OR
$("ul li:not(#one)").remove();
DEMO 2
EDIT
You need
var ulexceptOneLi = $("ul li:not(#one)");
or
var ulexceptOneLi = $("ul li").not($('#one'));

Try this code:
Fiddle
$(function(){
$("ul>li").not($('#one')).empty();
});

Assuming you meant to keep the ul in play:
$("ul li#one").remove();
Here's a fiddle...
If you're wanting to return a ul element with the removed element inside, try this:
function do_crazy_thing(){
var removed = $("ul li#one").remove();
return $('<ul></ul>').append(removed);
}
do_crazy_thing();
Here's another fiddle...
Here's how you would then append your new ul element to the body...

Demo Fiddle
According to your question, your expected output is :
<ul>
<li id='two'>Element 2</li>
<li id='three'>Element 3</li>
<li id='four'>Element 4</li>
<li id='five'>Element 5</li>
</ul>
Check the demo.
Edit :
$(function(){
var removed = $("ul li:not(#one)");
});
OR
var op = $("ul :not(#one)");

Please try below JS code
$(function(){
var test= $("ul li").remove("#one");
});

Replace href value by getting current URL

I have a menu in Wordpress that uses WP Menu system. All links are basically custom links that output the following (WP classes removed for brevity):
<ul>
<li>About
<ul>
<li>Section 1</li>
<li>Section 2</li>
<li>Section 3</li>
</ul>
</li>
<li>Services
<ul>
<li>Section 1</li>
<li>Section 2</li>
<li>Section 3</li>
<li>Section 4</li>
</ul>
</li>
</ul>
I'm trying to remove the domain part of the URL if the parent page is being viewed so if I were viewing the About page the links in the menu would change to:
<li>About
<ul>
<li>Section 1</li>
<li>Section 2</li>
<li>Section 3</li>
</ul>
</li>
<li>Services
<ul>
<li>Section 1</li>
<li>Section 2</li>
<li>Section 3</li>
<li>Section 4</li>
</ul>
</li>
</ul>
The problem I have with jQuery is that I cannot target each specific page because the pages will be unknown, I therefore need it to get the URL and match it with the correct part of the menu to change the links. I have tried this but its too specific:
if (window.location.href.indexOf("about") != -1) {
//do something
} else {
//do something else
}
EDIT
I only want to alter the links in the menu for the current page. The answers so far change all of the link in the menu, I just want to target the links found on the same page.

DEMO here
Firstly add a class sections to the ul element to make it easy to target.
<ul class="sections">
<li>Section 1
</li>
<li>Section 2
</li>
<li>Section 3
</li>
</ul>
Use .map() to replace the href for each anchor.
EDIT - based on your new update & I liked #Archer's update too. This should work.
$(".sections a[href* = '" + window.location.pathname + "/#']").map(function(){
var currentsection = this.href.split('/').pop();
this.href = currentsection;
});

Another option...
$(function() {
$("a[href*='" + window.location.pathname + "#']").attr("href", function() {
return "#" + this.href.split("#")[1];
});
});
This will find all the links with the current page and a # in them and fix the href value accordingly.

Try this,
$('a').each(function(){
// check the anchor tab href has location.href or not
if($(this).attr('href').indexOf(window.location.href) != -1)
{
// some code to replace location.href to blank
var href=$(this).attr('href').replace(window.location.href,'');
$(this).attr('href',href);
}
});
Alternatively, try this,
$('a').each(function(){
if(this.href.indexOf('#') != -1)
{
var href=this.href.split('#')[1];
this.href = '#'+href;
}
});

JQuery remove li based on ascii contents

I'm dynamically adding list items to a ul
<ul>
<li>thing 1</li>
<li>thing 2</li>
<li class='colorblock'>thing 3</li>
<li class='colorblock'>thing 4</li>
<li>thing 5</li>
</ul>
In some situations I need to enclose a few of the li with the following
$('.colorblock:first').before('<li>[± </li>');
$('.colorblock:last').append('<li>]</li>');
that products the following
<ul>
<li>thing 1</li>
<li>thing 2</li>
<li>[± </li>
<li class='colorblock'>thing 3</li>
<li class='colorblock'>thing 4</li>
<li>]</li>
<li>thing 5</li>
</ul>
now, if I also may need to remove those two li's with something along the following
$('li').filter(function() { return $.text([this]) === '[± '; }).remove();
$('li').filter(function() { return $.text([this]) === '[± '; }).remove();
$('li').filter(function() { return $.text([this]) === ']'; }).remove();
my problem is that none of these are correctly matching to
<li>[± </li>
I've ran out of ideas on how to strictly match and remove that li. any suggestions?

Try
$('li').filter(function(){
var txt = $.trim($(this).text());
return txt == '[±' || txt == ']'
}).remove()
Demo: Fiddle

Turns out it was an encoding issue with the file it was in, needed to be UTF-8