Develop Reference

Using JavaScript & jQuery in a single function (Nodes & Stuff)

I am currently learning jQuery. I know that jQuery is a custom library for JavaScript.
I am doing some learning examples in a book that is only using JavaScript, and to further my learning experience, I am trying to make use of jQuery for anything that might be more efficient.
So, I have this code:
function addLetter(foo) {
$(foo).unbind('click');
var tileLetter = $(foo).attr('class').split(' ');
var letter = tileLetter[2].charAt(1);
if (document.getElementById('currentWord').childNodes.length > 0) {
$('#currentWord p').append(letter);
} else {
var p = document.createElement('p');
var txt = document.createTextNode(letter);
p.appendChild(txt);
$('#currentWord').append(p);
}
}
Question #1:
If I change document.getElementById('currentWord').childNodes.length to $('#currentWord').childNodes.length it doesn't work. I thought the jQuery selector was the same thing as the JS document.getElementById as that it brought me back the DOM element. If that was the case, it'd make sense to be able to use the .childNodes.length functions on it; but it doesn't work. I guess it's not the same thing?
Question #2:
The code is textbook code. I have added all the jQuery that there is in it. My jQuery knowlede is limited, is there a more efficient way to execute the function?
The function's purpose:
This function is supposed to create a p element and fill it with a Text Node if it's the first time it's run. If the p element has already been created, it simply appends characters into it.
This is a word generating game, so you click on a letter and it gets added to a 'currentWord' div. The tile's letter is embedded in the 3rd css class, hence the attr splitting.
Thanks!

document.getElementById('currentWord')
returns a DOM object whereas $('#currentWord') returns a DOM object wrapped inside a jQuery object.
To get the plain DOM object you can do
$('#currentWord').get(0)
So
$('#currentWord').get(0).childNodes.length
should work.

Question #1:
jQuery returns a jQuery object. To return it to a regular javascript object use $(object)[0] and you can then treat it as a plain javascript (or DOM) object.
Question #2:
The efficiency looks good to me. Although you might want to use spans instead of p elements.
I guess one thing you could do (even though yours looks to run very fast) is cache the dom element:
function addLetter(foo) {
$(foo).unbind('click');
var tileLetter = $(foo).attr('class').split(' ');
var letter = tileLetter[2].charAt(1);
var currentWord = document.getElementById('currentWord');
if (currentWord.childNodes.length > 0) {
$(currentWord).find('p').append(letter);
} else {
var p = document.createElement('p');
p.innerHTML = letter;
currentWord.appendChild(p);
}
}

Calls to the jQuery() function ($()) return a jQuery object containing the matching elements, not the elements themselves.
Calling $('#some-id') will, then, return a jQuery object that contains the element that would be selected by doing document.getElementById('some-id'). In order to access that element directly, you can get it out of that jQuery object, using either the .get() function or an array index syntax: $('#some-id')[0] (it's 0-indexed).

I think you can replace all of this with a call to the text function.
function addLetter(foo) {
$(foo).unbind('click');
var tileLetter = $(foo).attr('class').split(' ');
var letter = tileLetter[2].charAt(1);
var currentWordP = $('#currentWord p');
if (currentWordP.size() > 0) {
currentWordP.text(currentWordP.text() + letter);
} else {
$('#currentWord').append("<p>" + letter + "</p>");
}
}

1: Use $.get(0) or $[0] to get the DOM element. e.x. $('#currentWord')[0].childNodes.length.
2: Try this:
function addLetter(foo) {
$(foo).unbind('click');
var tileLetter = $(foo).attr('class').split(' ');
var letter = tileLetter[2].charAt(1);
if ($('#currentWord p').length > 0) {
$('#currentWord p').append(letter);
} else {
$('#currentWord').append(
$('<p />', { text: letter })
);
}
}

Question #1:
document.getElementById returns DOM object. more
childNodes.length is property of Node object which is returned by document.getElementById.
jQuery selector returns jQuery object more. You can get DOM object from jQuery object using .get
$('#IDselector').get(0) = document.getElementById('IDselector')
Question #2:
function addLetter(foo) {
$(foo).unbind('click');
var tileLetter = $(foo).attr('class').split(' ');
var letter = tileLetter[2].charAt(1);
if ($('currentWord p').length > 0) {
$('#currentWord p').append(letter);
} else {
var p = $('<p />').text(letter);
$('#currentWord').append(p);
}
}

access divs of same class name using javascript

I have the following html code-
<div class="search_results">...</div>
<div class="search_results">...</div>
<div class="search_results">...</div>
The divs are automatically generated by a javasciprt function. Is there a way to access only the first div/or a specific div of the same class name "search_results" with javascript?

If you use JQuery $(".search_results").first(). Else you need to use document.getElementsByClassName("search_results")[0];

You can use getElementsByClassName which returns a NodeList (which is an array-like object). You can then access individual elements of that using normal array syntax. This example will return the first element:
var firstDiv = document.getElementsByClassName("search_results")[0];
Or, you could use querySelector, which returns the first element found:
var firstDiv = document.querySelector(".search_results");
If you want to return all matched elements, you can use querySelectorAll, which returns a NodeList, like getElementsByClassName.

Use getElementsByClassName or querySelector (if available):
function findElementsByTagNameAndClassName(tag, class_name) {
if(typeof document.querySelector !== 'undefined') {
return document.querySelector(tag + ' .' + class_name);
}
var els = document.getElementsByClassName(class_name);
var result = [];
for(var i = 0; i < els.length; ++i) {
if(els[i].nodeName === tag) {
result.push(els[i]);
}
}
return result;
}
var firstDiv = findElementsByTagNameAndClassName('div', 'search_results')[0];

If you're using JQuery:
$("div.search_results").first() for later versions of JQuery and $("div.search_results")[0] for older ones.
No Jquery:
document.getElementsByClassName

If you want to access a specific instance, you will want to add an id attribute to the elements, for example:
<div class="search_results" id="result_1">...</div>
<div class="search_results" id="result_2">...</div>
<div class="search_results" id="result_3">...</div>
If that's not an option, you can access the n'th item with the classname (starting from 0) using
var divN = document.getElementsByClassName("search_results")[n];

Getting element by a custom attribute using JavaScript

I have an XHTML page where each HTML element has a unique custom attribute, like this:
<div class="logo" tokenid="14"></div>
I need a way to find this element by ID, similar to document.getElementById(), but instead of using a general ID, I want to search for the element using my custom "tokenid" attribute. Something like this:
document.getElementByTokenId('14');
Is that possible? If yes - any hint would be greatly appreciated.
Thanks.

It is not good to use custom attributes in the HTML. If any, you should use HTML5's data attributes.
Nevertheless you can write your own function that traverses the tree, but that will be quite slow compared to getElementById because you cannot make use of any index:
function getElementByAttribute(attr, value, root) {
root = root || document.body;
if(root.hasAttribute(attr) && root.getAttribute(attr) == value) {
return root;
}
var children = root.children,
element;
for(var i = children.length; i--; ) {
element = getElementByAttribute(attr, value, children[i]);
if(element) {
return element;
}
}
return null;
}
In the worst case, this will traverse the whole tree. Think about how to change your concept so that you can make use browser functions as much as possible.
In newer browsers you use of the querySelector method, where it would just be:
var element = document.querySelector('[tokenid="14"]');
This will be much faster too.
Update: Please note #Andy E's comment below. It might be that you run into problems with IE (as always ;)). If you do a lot of element retrieval of this kind, you really should consider using a JavaScript library such as jQuery, as the others mentioned. It hides all these browser differences.

<div data-automation="something">
</div>
document.querySelector("div[data-automation]")
=> finds the div
document.querySelector("div[data-automation='something']")
=> finds the div with a value

If you're using jQuery, you can use some of their selector magic to do something like this:
$('div[tokenid=14]')
as your selector.

You can accomplish this with JQuery:
$('[tokenid=14]')
Here's a fiddle for an example.

If you're willing to use JQuery, then:
var myElement = $('div[tokenid="14"]').get();

Doing this with vanilla JavaScript will do the trick:
const something = document.querySelectorAll('[data-something]')

Use this more stable Function:
function getElementsByAttribute(attr, value) {
var match = [];
/* Get the droids we are looking for*/
var elements = document.getElementsByTagName("*");
/* Loop through all elements */
for (var ii = 0, ln = elements.length; ii < ln; ii++) {
if (elements[ii].nodeType === 1){
if (elements[ii].name != null){
/* If a value was passed, make sure it matches the elements */
if (value) {
if (elements[ii].getAttribute(attr) === value)
match.push(elements[ii]);
} else {
/* Else, simply push it */
match.push(elements[ii]);
}
}
}
}
return match;
};

jquery, how to check if a specific ID is a child of an other id?

I have a specific id ("mysubid"), now I want to check if this element (this id) is in a child path of an other id ("mymainid").
Is there an easy way to do this or will I go upwards, element by element, to see if the element is in a child path.
By child path I am talking about something like this:
A > B > C > D
So D is in the Child Path of A,B and C

You all are making this very complicated. Use the descendant selector:
if ($('#mymainid #mysubid').length) {
// #mysubid is inside #mymainid
}

var isInPath = $("#mysubid").closest("#mymainid").length > 0;

if( $("#mymainid").find("#mysubid").length > 0 )

if($('#mysubid','#mymainid').length)
{
}
This will check to see if #mysubid is within #mymainid
jQuery( selector, [ context ] )
selector: A string containing a selector expression
context: A DOM Element, Document, or jQuery to use as context
This is a just an overlaod for $('#mymainid').find('#mysubid').lentgh btw, verified from: http://github.com/jquery/jquery/blob/master/src/core.js#L162
On another note, using a method such as $('#a #b') resorts to using the Sizzle Selector witch is slower than doing $('#a',$('#b')), witch uses purely javascript's getElementById
Note: as jQuery returns an empty object by default if the selection is not found you should always use length.

If you want to see the entire chain as an array use elm.parentNode and work backwards. So, to answer your question (and the depth or distance between the elements) in POJ, you can use:
var doc = document,
child = doc.getElementById("mysubid"),
parent = doc.getElementById("mymainid"),
getParents = function (elm) {
var a = [], p = elm.parentNode;
while (p) {
a.push(p);
p = p.parentNode;
}
return a;
};
getParents(child).indexOf(parent);

I tried on various browsers and the DOM function below is between 3 to 10 times faster than the selector methods(jQuery or document.querySelectorAll)
function is(parent){
return {
aParentOf:function(child){
var cp = child.parentNode;
if(cp){
return cp.id === parent.id ?
true : is(parent).aParentOf(cp);
}
}
}
}
The call below will return true if A is a parent of D
is(document.getElementById('A')).aParentOf(document.getElementById('D'))
For just few calls I would use the $('#A #D').length
For very frequent calls I would use the DOM one.

Using the 'is' method actually returns a boolean.
if($('#mymainid').is(':has(#mysubid)')) // true
Going the other direction...
if($('#mysubid').parents('#mymainid').length) // 1

Get class list for element with jQuery

Is there a way in jQuery to loop through or assign to an array all of the classes that are assigned to an element?
ex.
<div class="Lorem ipsum dolor_spec sit amet">Hello World!</div>
I will be looking for a "special" class as in "dolor_spec" above. I know that I could use hasClass() but the actual class name may not necessarily be known at the time.

You can use document.getElementById('divId').className.split(/\s+/); to get you an array of class names.
Then you can iterate and find the one you want.
var classList = document.getElementById('divId').className.split(/\s+/);
for (var i = 0; i < classList.length; i++) {
if (classList[i] === 'someClass') {
//do something
}
}
jQuery does not really help you here...
var classList = $('#divId').attr('class').split(/\s+/);
$.each(classList, function(index, item) {
if (item === 'someClass') {
//do something
}
});

Why has no one simply listed.
$(element).attr("class").split(/\s+/);
EDIT: Split on /\s+/ instead of ' ' to fix #MarkAmery's objection. (Thanks #YashaOlatoto.)

On supporting browsers, you can use DOM elements' classList property.
$(element)[0].classList
It is an array-like object listing all of the classes the element has.
If you need to support old browser versions that don't support the classList property, the linked MDN page also includes a shim for it - although even the shim won't work on Internet Explorer versions below IE 8.

Here is a jQuery plugin which will return an array of all the classes the matched element(s) have
;!(function ($) {
$.fn.classes = function (callback) {
var classes = [];
$.each(this, function (i, v) {
var splitClassName = v.className.split(/\s+/);
for (var j = 0; j < splitClassName.length; j++) {
var className = splitClassName[j];
if (-1 === classes.indexOf(className)) {
classes.push(className);
}
}
});
if ('function' === typeof callback) {
for (var i in classes) {
callback(classes[i]);
}
}
return classes;
};
})(jQuery);
Use it like
$('div').classes();
In your case returns
["Lorem", "ipsum", "dolor_spec", "sit", "amet"]
You can also pass a function to the method to be called on each class
$('div').classes(
function(c) {
// do something with each class
}
);
Here is a jsFiddle I set up to demonstrate and test http://jsfiddle.net/GD8Qn/8/
Minified Javascript
;!function(e){e.fn.classes=function(t){var n=[];e.each(this,function(e,t){var r=t.className.split(/\s+/);for(var i in r){var s=r[i];if(-1===n.indexOf(s)){n.push(s)}}});if("function"===typeof t){for(var r in n){t(n[r])}}return n}}(jQuery);

You should try this one:
$("selector").prop("classList")
It returns a list of all current classes of the element.

var classList = $(element).attr('class').split(/\s+/);
$(classList).each(function(index){
//do something
});

$('div').attr('class').split(' ').each(function(cls){ console.log(cls);})

Update:
As #Ryan Leonard pointed out correctly, my answer doesn't really fix the point I made my self... You need to both trim and remove double spaces with (for example) string.replace(/ +/g, " ").. Or you could split the el.className and then remove empty values with (for example) arr.filter(Boolean).
const classes = element.className.split(' ').filter(Boolean);
or more modern
const classes = element.classList;
Old:
With all the given answers, you should never forget to user .trim() (or $.trim())
Because classes gets added and removed, it can happen that there are multiple spaces between class string.. e.g. 'class1 class2 class3'..
This would turn into ['class1', 'class2','','','', 'class3']..
When you use trim, all multiple spaces get removed..

Might this can help you too. I have used this function to get classes of childern element..
function getClickClicked(){
var clickedElement=null;
var classes = null;<--- this is array
ELEMENT.on("click",function(e){//<-- where element can div,p span, or any id also a class
clickedElement = $(e.target);
classes = clickedElement.attr("class").split(" ");
for(var i = 0; i<classes.length;i++){
console.log(classes[i]);
}
e.preventDefault();
});
}
In your case you want doler_ipsum class u can do like this now calsses[2];.

Thanks for this - I was having a similar issue, as I'm trying to programatically relate objects will hierarchical class names, even though those names might not necessarily be known to my script.
In my script, I want an <a> tag to turn help text on/off by giving the <a> tag [some_class] plus the class of toggle, and then giving it's help text the class of [some_class]_toggle. This code is successfully finding the related elements using jQuery:
$("a.toggle").toggle(function(){toggleHelp($(this), false);}, function(){toggleHelp($(this), true);});
function toggleHelp(obj, mode){
var classList = obj.attr('class').split(/\s+/);
$.each( classList, function(index, item){
if (item.indexOf("_toggle") > 0) {
var targetClass = "." + item.replace("_toggle", "");
if(mode===false){$(targetClass).removeClass("off");}
else{$(targetClass).addClass("off");}
}
});
}

Try This. This will get you the names of all the classes from all the elements of document.
$(document).ready(function() {
var currentHtml="";
$('*').each(function() {
if ($(this).hasClass('') === false) {
var class_name = $(this).attr('class');
if (class_name.match(/\s/g)){
var newClasses= class_name.split(' ');
for (var i = 0; i <= newClasses.length - 1; i++) {
if (currentHtml.indexOf(newClasses[i]) <0) {
currentHtml += "."+newClasses[i]+"<br>{<br><br>}<br>"
}
}
}
else
{
if (currentHtml.indexOf(class_name) <0) {
currentHtml += "."+class_name+"<br>{<br><br>}<br>"
}
}
}
else
{
console.log("none");
}
});
$("#Test").html(currentHtml);
});
Here is the working example: https://jsfiddle.net/raju_sumit/2xu1ujoy/3/

For getting the list of classes applied to element we can use
$('#elementID').prop('classList')
For adding or removing any classes we can follow as below.
$('#elementID').prop('classList').add('yourClassName')
$('#elementID').prop('classList').remove('yourClassName')
And for simply checking if the class is present or not we can use hasClass

I had a similar issue, for an element of type image. I needed to check whether the element was of a certain class. First I tried with:
$('<img>').hasClass("nameOfMyClass");
but I got a nice "this function is not available for this element".
Then I inspected my element on the DOM explorer and I saw a very nice attribute that I could use: className. It contained the names of all the classes of my element separated by blank spaces.
$('img').className // it contains "class1 class2 class3"
Once you get this, just split the string as usual.
In my case this worked:
var listOfClassesOfMyElement= $('img').className.split(" ");
I am assuming this would work with other kinds of elements (besides img).
Hope it helps.

javascript provides a classList attribute for a node element in dom. Simply using
element.classList
will return a object of form
DOMTokenList {0: "class1", 1: "class2", 2: "class3", length: 3, item: function, contains: function, add: function, remove: function…}
The object has functions like contains, add, remove which you can use

A bit late, but using the extend() function lets you call "hasClass()" on any element, e.g.:
var hasClass = $('#divId').hasClass('someClass');
(function($) {
$.extend({
hasClass: new function(className) {
var classAttr = $J(this).attr('class');
if (classAttr != null && classAttr != undefined) {
var classList = classAttr.split(/\s+/);
for(var ix = 0, len = classList.length;ix < len;ix++) {
if (className === classList[ix]) {
return true;
}
}
}
return false;
}
}); })(jQuery);

The question is what Jquery is designed to do.
$('.dolor_spec').each(function(){ //do stuff
And why has no one given .find() as an answer?
$('div').find('.dolor_spec').each(function(){
..
});
There is also classList for non-IE browsers:
if element.classList.contains("dolor_spec") { //do stuff