Develop Reference

Is there a way to Hide/unhide all child elements of a DOM node in JavaScript?

Say I have the following HTML and I want to hide all the children of the 'overlay' div dynamically
<div id="overlay" class="foo">
<h2 class="title">title</h2>
<h1 id="bar">sub-title</h1>
<button id="reset">reset</button>
</div>
is there a better way to mass hide/unhide these elements than calling .className = 'hide' on them individually?
*note that I want to retrieve those later so looping over them with .remove() or setting div innerHTML to an empty string is not an option

In your css you can create this:
#overlay.hidden-content > * {
visibility: hidden
}
And add hidden-content to your div with overlay id to hide all the child elements.

Select first child elements of multiple parent elements and apply same class to all

I'm looking for a way to select the first child element of multiple parent divs, of which the parent divs have the same class. This is my HTML:
<div class="wrapper">
<p>Select this paragraph</p>
</div>
<div class="wrapper">
<img src="https://picsum.photos/200/300" title="Select this image">
<p>Don't select this</p>
</div>
<div class="wrapper">
<p>Select this paragraph</p>
<p>Don't select this paragraph</p>
</div>
Please see my full CodePen Here.
I'm trying to select the first child element of each div with the class wrapper and apply the same class to all of these child elements. I was looking at something in the lines of this:
$('.wrapper').children(":first").addClass("noMargin");
The problem with this is that it only selects the child element of the first parent div, but it doesn't select the img and the first p of the third wrapper. I figured you need some kind of array for this and apply a class to all of them, but how can I achieve this (with preferably jQuery)?

You're close, what you need is to go through the elements that have the .wrapper class and append the noMargin class to their first children i.e
$('.wrapper').each(function() {
$(this).children(":first").addClass("noMargin");
});

you can use following sample it is working fine
$('.wrapper :nth-child(1)').addClass("noMargin");
or another syntax
$('.wrapper :first-child').addClass('noMargin');

jQuery - How to hide an element and its children?

I have a div which I would like to hide along with all of its children. I thought that a simple selector.hide() would do the trick but it's still there.
HTML
<div class="row well">
<div class="artistAlbumInfo well col-md-6 ">
<h3><span id="artist"></span> - <span id="track"></span></h3>
<img src="" id="art" class="albumArt">
</div>
<div class="col-md-6">
<h3 id="album"></h3>
<h4>Playstate <p id="playState"></p></h4>
<h4>Position <p id="position"></p></h4>
</div>
</div>
JQuery
$(document).ready(function() {
$('.row .well').hide();
});
http://jsfiddle.net/375c8v2a/1/
Any ideas?

You don't need a space between classes if you want to hide only those with both classes
$('.row.well').hide();
To do either or add a comma
$('.row, .well').hide();

What you have didn't work because .row .well means "an element with class well inside (as a child or deeper descendant) an element with class row. In CSS, the space is the descendant combinator.
To seelct the element that has both classes, remove the space:
$(document).ready(function() {
$('.row.well').hide();
// ----^
});
That means "an element with class row and class well".

$('.row').hide();
please remove second class

From what I've read on the comments the .well class was intentionally created to specify which .row class will be hiding since you have a lot of row classes. Then you can use it as the trigger to hide that row, instead of doing: $('.row.well').hide(); you can just simply specify the targeted class by doing:
$('.well').hide();
Click here to see a example on jsFiddle

JQuery. Remove a previous sibling in the DOM tree

I have the next code dynamically created using JQuery. Theere are multiple row class divs placed one under the other.
<div class="row">
....
</div>
<div class="row">
<div class="line_type"></div>
<div class="download_value"></div>
<div class="flag"></div>
<div class="email"></div>
<div class="prize"></div>
</div>
<div class="row">
....
</div>
After i create these divs I have a "pointer" to a specific div which is of class row. In JQuery, how do i make it so I go down the DOM tree, until i reach the div of class line_type and download_value and remove them both, and also I'd like to go one more node down, at the div of type email and change some of it's CSS attributes.
I was not able to find anything on the web, maybe it's cause i'm a noob at these still.

I have a "pointer" to a specific div which is of class row ->
Assuming that you have the this object of the corresponding div with class row.. then you can use .find to get the line_type and download_value inside that div.
$(this).find('.line_type').remove();
$(this).find('.download_value').remove();
Then you can use the same .find to get the div with class email and access the .css
$(this).find('.email').css(/* You code*/);

Assuming row_pointer points to the row in question:
$('.line_type, .download_value', row_pointer).remove();
$('.email', row_pointer).css(...);

check this out
$('div.row').bind('click', function() {
$this = $(this);
$('div.line_type, div.download_value', $this).remove();
$('div.email', $this).css('background-color', 'red');
});
http://jsfiddle.net/YvyE3/

multiple onclick's in HTML

I have a an HTML page with a list of 20 topics on it. I would like it so that when you click on one of those topics, 2 or 3 articles with links pop up underneath it.
I'm trying onclick but it means writing lots of code as you have to declare all the div styles for each of my topics.
Is there an easy way of doing this?
im currently writing this 20 times, and declaring 60 div styles:
<div class = "mousehand"
id = "show_first"
onclick ="this.style.display = 'none';
document.getElementById('show_second').style.display='block';
document.getElementById('dropdown').style.display='inline';
"> show text </div>
<div class = "mousehand"
id = "show_second"
onclick ="this.style.display = 'none';
document.getElementById('show_first').style.display='block';
document.getElementById('dropdown').style.display='none';
"> hide text </div>
<div id ="dropdown"> this is the text to be shown</div>

You can accomplish this with some Javascript. Add a ul within the li:
<li>Title
<ul>
...
</ul>
</li>
Set the inner ul's display to none using CSS. Then using Javascript, make a function that changes the display property of the inner ul to block.

As has been mentioned, jQuery can make this very straightforward, but your major code saving is going to come from taking advantage of event bubbling. You can do this is you structure your HTML something like this:
<div id="topics">
<div class="item">
<div class="show">
show text 1
</div>
<div class="hide">
hide text 1
</div>
<div class="text">
this is the text to be shown 1
</div>
</div>
<div class="item">
<div class="show">
show text 2
</div>
<div class="hide">
hide text 2
</div>
<div class="text">
this is the text to be shown 2
</div>
</div>
</div>
Now instead of attaching an onclick handler to each end every div, attach it to the parent element. To do this with jQuery:
$(window).load(function(){ //Do this when the page loads
$('#topics').bind('click', function(event) { //Find the element with ID 'topics' and attach a click handler
var t = $(event.target); //event.target is the element that was actually clicked, $() gets the jQuery version of it
if(t.hasClass('show')) { //If it is a 'show' element...
t.siblings('.hide').show(); //...show the other two elements...
t.siblings('.text').show();
t.hide(); //...and hide the clicked element
}
if(t.hasClass('hide')) { //If it is a 'hide' element...
t.siblings('.show').show(); //...show the 'show' element...
t.siblings('.text').hide(); //...and hide the other two
t.hide();
}
});
});
And that's it! Here's a demo.