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JavaScript equivalent to JQuery .next()

Is there a JavaScript method similar to jQuery .next()? I want to find the next element that has the class of "error" relative to the element. I've tried using .nextSibling as a loop but couldn't figure it out. Didn't know if there was an easier way to go about it without jQuery.
For instance, if I have this code:
<div id="section">
<div id="test">test</div>
<span class="info">Information</span>
<span class="error">Error!</span>
</div>
I'm trying to get the next .error class closest to #test, if I have a #section2 and a #test2 I would want to get the .error class closest to #test2 and so on.

The nextElementSibling property returns the element immediately following the specified element, in the same tree level.
Example: Get the HTML content of the next sibling of a list item:
var x = document.getElementById("item1").nextElementSibling
The nextElementSibling property might help.

Best bet would be to search through the jQuery code and see what they did.
http://code.jquery.com/jquery-2.0.3.js
At a glance, I do see some calls to "nextSibling" and "previousSibling."
Also see here:
How to get next element using JavaScript-only?
Hope this helps!

This is the pure javascript for you:
HTML
<div id="nodes">
<div class="error">This is error Node</div>
<div class="nextElement">This is next Element</div>
</div>
Javscript:
var nodes = Array.prototype.slice.call( document.getElementById('nodes').children ),
errorNode = document.getElementsByClassName('error')[0];
var indexOfError = nodes.indexOf(errorNode);
var nextElement = nodes[indexOfError + 1];
alert(nextElement.innerText);
Here is demo

Sounds like you may be looking for document.getElementsByClassName()... if the elements with class=error are not direct siblings in the DOM, then there's not a good way to find them otherwise. It's elementary, but you can just search through the array returned by document.getElementsByClassName('error') until you find your starting element, and then you know the next item in the array will be the next element in the DOM.
See also MDN reference. Won't work in old IE, but works for all modern browsers.

Appending a div on unknodw div

I have three divs. How should I append a div onto an unknown div?
<div class="main" >
<div id="drag-box" >
<div id="" class=""> </div>
</div>
</div>
I want to append div on an unknown div which is come after drag-box div. I don't know which div comes after drag-box div. But there must be one div after drag-box div.

$("#drag-box div:first-child").append("<span />");
or
$("#drag-box div").first().prepend("<span>first</span>");
For a complete answers, here it is working:
http://jsfiddle.net/dMUD3/

try this
$("#drag-box div:first-child").attr("id");

Instead of giving you a one liner I would like to give you an indepth solution.
A browser takes your html and parses what is called a DOM Tree out of it.
so if your html is .
<div class="a">
<div class="foo"></div>
<button class="foogle"></button>
</div>
The tree structure will become something like
`-div.a
|-div.foo
`Button.foogle
You should actually look into DOM Api's at MDN
How DOM helps ?
With DOM api's you can actually access the unknown div using the reference to a known div. So if you actually understand your markup and its representation in DOM it should be pretty simple to get reference to nth child of an element;
You can access the child elements by the children attribute.
So
// Get reference to the element.
var parent = document.getElementById("drag-box");
// Use the dom.
var child_i_want = parent.children[0];
// or there is another way
var child_i_reallyWant = parent.firstElementChild;
There are solutions with jQuery but I feel its important for you to Understand basics of DOM even when there are helpful abstraction libraries in existance.

You'll need the + selector. It applies to the object directly following. See here.
.drag-box + div {
}

$('<div></div>').appendTo($('#drag-box div:first'))

Get Text Of Closest Parent H4 Using Jquery

I have several of these html blocks on a page in this structure
<div class="listing">
<h4>Some test Entry here</h4>
<div class="entry clearfix">
<a href="#" class="btn">
Text Here
</a>
</div>
</div>
I have the click event on the '.entry .btn' which is firing fine. But I want to get the inner text of the 'H4 a' within the same listing block as the btn I clicked. I have tried the following but just cannot seem to get the H4 text.
var getTitle = $(this).parents("h4").first();
alert(getTitle.html());
I have also tried closest() but still cannot get the H4? Any ideas?

closest & parents looks for ancestors. But, h4 is in another children of parent .listing.
Try:
var getTitle = $(this).closest('.listing').find("h4").first();

Firstly You need to traverse upwards in the DOM structure to identify the target element using .parent() or .parents() functions.
For your requirement you dont need the immediate parent hence .parent() is of no use instead you need to use .parents() to get all the ancestors in the DOM and refer the one with class selector .listing & finally traverse inward to find the target element h4.
JS CODE:
$('.btn').on('click',function(){
alert($(this).parents('.listing').find('h4').html());
});
Live Demo # JSFIDDLE
Happy Coding :)

use prev function in jquery
var getTitle = $(this).prev().find("h4").first();
alert(getTitle.html());

Is there any way we can do append on the next element？

Like, we have <div id='target'></div><div id='footer'></div>
i just want to append <div id='target'></div> , the result will be like
<div id='target'></div><div id='target'></div><div id='footer'></div>
append just append something inside the element,
is there any Jquery method i can do this

Try this:
$("div#target").after($("div#target").clone());
Hope this will help.

$('<div />').after($('#target'))
IDs must be unique, otherwise you will have lots of problems with your selectors later on. The solution above will create a new div element and apend it after your #target

jQuery('<div />').after('div#targetdiv')

How can I say this in jQuery?

I want to append some text after 2 closing divs to a sector element.
Click me
</div>
</div>
// this is where I want to append the text
My code appends the text after the link. How can I say "append it after the 2nd closing div"?
$('a.thingIClicked').click(function() {
$(this).append('hello');
});

The most direct way to do this is to find the second parent <div> element, and then insert the text after it.
$('a.thingIClicked').click(function() {
$(this).parent("div").parent("div").after("some text");
});
This will insert the text on the outside of the second <div> parent. Using append() will put the text on the inside of the parent, which from your example doesn't appear to be what you want.

There's probably a more elegant solution, but how about:
$('a.thingIClicked').click(function() {
$(this).parent().parent().after('hello');
});
Edit: #Zack is correct (and should probably get the answer credit for this one) - my original code would have added the text into the second enclosing div, rather than after it. I've edited my code above accordingly.

The easiest way would be to give the outer div an id and then use $("#outerdivid").
EDIT: Below will not work, but leaving it here for reference
However, you should also be able to use a jquery :parent filter:
http://api.jquery.com/filter/
$('a.thingIClicked').filter(':parent').filter(':parent').click(/**/);

Use .insertAfter()
http://api.jquery.com/insertAfter/
<div class="container">
<h2>Greetings</h2>
<div>Hello</div>
<div class="inner">Goodbye</div>
</div>
We can create content and insert it after several elements at once:
$('<p>Test</p>').insertAfter('.inner');

Use .insertAfter() - http://api.jquery.com/insertAfter/
<div class="container">
<h2>Greetings</h2>
<div>Hello</div>
<div class="inner">Goodbye</div>
</div>
We can create content and insert it after several elements at once:
$('<p>Test</p>').insertAfter('.inner');