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How to delete current element if previous element is empty in jquery?

I want to delete element with class "tehnicneinfo" but only if the element I'm checking ( with class "h2size") has no child. I have a bunch of those elements, generated by a plugin and I want to delete only the ones that have the next element without child. I wrote jquery code, but it delets all of my elements, not only the ones that have the next element without child. Here is my jquery code:
$('.news .h2size > div').each(function() {
var ul = $(this).find('ul');
if(!ul.length) $(this).remove();
var h1 = $('.news').find('.tehnicneinfo');
var h2size = $('.news').find('.h2size');
if(h2size.prev().is(':empty'))
{
h1.remove();
}
});
this code is inside $(document).ready(function(). Can you tell me what I'm doing wrong? The code is for something else also, so I'm having truble only from var h1 = $('.news').find('.tehnicneinfo'); this line on. Thanks in advance!
Html:
<div class="news">
<h1 class="tehnicneinfo">xxx</h1>
<div class="h2size">
<div id="xyxyxy">
.......
</div>
</div>
<h1 class="tehnicneinfo">yyy</h1>
<div class="h2size"></div>
....
</div>
That's the html, only that there is like 20 more lines that are the same, but with different values (not yyy and xxx). I would need to delete all 'yyy' (they are not all with same value).

You can use filter to filter the ones you want to remove then remove them
"I want to delete only the ones that have the next element without child"
$('.tehnicneinfo').filter(function(){
return !$(this).next().children().length;
// only ones with next sibling with no children
}).remove();
JSFIDDLE

Select DIV using its ID + addition

Using a div as selector is easy:
<div id="test1"></div>
$('#test1').doSomething();
I want to target only another div, containing the same ID + _sub:
<div id="test1"></div>
<div id="test1_sub"></div>
$('#test1').find( /* Same ID + "_sub" */ ).doSomething();
How can I do this? I know I can use .attr('id') to take #test1, but I do not how to extend this with _sub.
JS FIDDLE
Of course it would be easy to target the #test1_sub directly, but image I have 1000 divs counting up test1, test2, test3, etc. and want to use this inside of a function.

You do it like this
$('#test1' + "_sub").fadeOut();
Note the quotation-marks containing "_sub".
EDIT: In your answer, you made up an example where you had 100 divs with ids like test1, test2 and so on. Then you could select all elements with an id beginning with test. Like this:
$('*[id^="test"]').fadeOut();

Here you can use start with selector to work with all ids.
jsFiddle
$(document).ready(function(){
$( "*[id^='test1']" ).fadeOut();
})
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.0/jquery.min.js"></script>
<div id="test1">Test 1</div>
<div id="test1_sub"> Test 1 Sub</div>
<div id="test1_asdf">Test 1 ASDF</div>
<div id="test1_sub342"> Test 1 sub342</div>
<div id="test1_sdfsd">Test 1 sdfsd</div>
<div id="test1_45645"> Test 1 45645</div>

Set a variable and chain: (CORRECTED)
var target = $(whatever test div you targetted).attr('id');
$('#'+target + "_sub").doSomething();
You said you were going to use it in a function, so it would be targettable this way for example. Lets say when you click #test1 a function will run on all subs based on the clicked test:
$('.testBoxes').click(function () {
var target = $(this).attr('id');
$('#'+target + "_sub").doSomething();
});

How to get id's of multiple divs on clicking one div

I have following code
<div id = "fa10_holder">
<div id = "b-1"></div>
</div>
I am adding this dynamically in a div that holds all of these type of divs ..
lets say if I add another div it would be like this
<div id = "fa11_holder">
<div id = "b-2"></div>
</div>
Now the problem is when I click the div with id of b-1 or b-2 and so on I want the id of its parent like fa10_holder and the id of the clicked div aswell... can any one help me ??

Like this working demo another way.
APIs:
parents - http://api.jquery.com/parents/
attr or prop - http://api.jquery.com/attr/ or http://api.jquery.com/prop/
I have added extra class, in case you have many div you can have a blanket click via class. :)
Extra: When to access the attribute (vs the property)?
code
$(document).ready(function () {
$(".hulk").click(function () {
alert($(this).parents('div').attr('id'));
alert($(this).attr('id'));
});
});
html
<div id = "fa11_holder"> parent
<div id = "b-2" class="hulk">hulk</div>
</div>

var thisid = this.id;
var parrentid = $(this).parent().attr('id');

Find followers of an element in a certain scope, which aren't siblings

I am trying to select all following elements of an element I choose. They don't necessarily have to be direct siblings of my chosen Element, so .nextAll() won't work.
Here's an example:
<div class="scope">
<div> 1 </div>
<div> 2 </div>
<div> 3 </div>
<div> 4 </div>
</div>
NOT THIS
My element is a[href="2"], so I want to select a[href="3"] and a[href="4"], but not a[href="x"] because it's not in my scope.
I found this, but it only fetches one follower, but I need all of them.
I just wrote this, which works great, but it seems odd to me and I am sure that there have to be better solutions than this one:
var $two = $('a[href="2"]');
var selection = [];
var comes_after_2 = false;
$two.closest('.scope').find('a').each(function(){
console.log(this, $two.get(0));
if(comes_after_2){
selection.push(this);
}
if(this == $two.get(0)){
comes_after_2 = true;
}
});
$(selection).css('background', 'red');
Here is a Fiddle to test it: http://jsfiddle.net/mnff40fy/1/
Please feel free to modify it, if there's a better solution. Thank you!

var $all_a = $two.closest('.scope').find('a');
// Get the position of the selected element within the set
var a_index = $all_a.index($two);
// Select all the remaining elements in the set
var $followers = $all_a.slice(a_index+1);
$followers.css('background', 'red');
DEMO

How about this?
JSFiddle
I changed the markup a little to have the href='#' so you could click each one and see how the other elements respond.
$('a').click(function(){
$('a').css('background', 'none');
var scopeDiv = $(this).closest('div.scope');
var thisIndex = $(scopeDiv).find('a').index(this);
$(scopeDiv).find('a').not(this).each(function(index){
if(index >= thisIndex)
$(this).css('background', 'red');
});
});

As an alternative, you can use .nextAll() if you modify it a bit.
In your html code, you placed the a elements as children of the div tags. In order to incorporate .nextAll() you should select for the wrapper div elements and then call .nextAll() and then select for the children a elements.
Here is what I mean.
html
<div class="scope">
<div>
1
</div>
<!-- Start Here -->
<div class="start">
2
</div>
<div>
3
</div>
<div>
4
</div>
</div>
NOT THIS
js
$( '.start' ).nextAll().children( 'a' ).css( 'background-color', 'red' );
Explanation:
I select the wrapper div with $( '.start' )
I then select all of its subsequent siblings with .nextAll()
Of those siblings, I select their children that match 'a'
I apply the css
And here is the Fiddle

Empty parent DIV but not child div

I have two divs included one in the other:
<DIV id="DIV_1">
parent_contents
parent_contents
<DIV id="DIV_2">
child_contents
child_contents
</DIV>
</DIV>
I want to remove parent_contents, but not the child_contents. When I do:
$('#DIV_1').remove();
I lose the child contents...

Filter out the textnodes and remove them :
$('#DIV_1').contents().filter(function() {
return this.nodeType === 3;
}).remove();
FIDDLE
or to leave just #DIV_2, filter out just that one element:
$('#DIV_1').contents().filter(function() {
return this.id != 'DIV_2';
}).remove();
FIDDLE

I'm pretty sure one of the easiest ways would be to copy the DIV_2 child content into a variable, then simply append it to DIV_1 after emptying it.
jsFiddle DEMO
var $temp = $('#DIV_2');
$("#DIV_1").empty().append($temp);