Best practice in finding a DOM element - javascript

I want to toggle(hide/show) an element when a button is being pressed. I have two ways as to implement this:
Find the element according to its class name, e.g $('.my-content')
Find the element according to its relevant DOM position towards the button, e.g. $('#my-button').parent().next().next().next()
However, none of the above seems to me very reliable since in case someone changes the HTML code, the above approaches should not work. Is there something more reliable I am missing?

If it's a specific element, supply it with an Id value and use that
to find it.
If it's a TYPE of element, use a class name.
Other than that, there's no real conventions. Just try and make sure that somebody reading your code understands what is going on.

A very good practice is to decouple HTML, CSS and JS.
When binding javascript to DOM elements you should use javascript selectors.
Basically classes with some custom prefix (like js-) which will be used only for javascript purposes (not css style).
So whenever the DOM tree structure or the CSS class names are changed, you can still have your working JS selector
HTML
<div class="my-content js-toggle-element"></div>
JS
$('.js-toggle-element')
CSS
.my-content{ ... }
Plus, using Javascript Selectors:
makes HTML highly readable: you can easily find out what will happen to that element with that js class
allows you to easily apply/disapply that behaviour also to other elements in the future, simply by adding/removing that class in your HTML and without affecting CSS at all
<div class="my-content js-toggle-element"></div>
...
<div class="another-content-to-toggle js-toggle-element"></div>

Using jQuery will be much easiest way. Like this -
$( ".target" ).toggle();
The matched elements will be revealed or hidden immediately, with no animation, by changing the CSS display property. If the element is initially displayed, it will be hidden; if hidden, it will be shown.
Reference - jQuery Toggle

If the class or the position of the element in DOM is changing then you can try
selecting it with the inner text
$("button:contains('buttontextgoeshere')")

Related

Is there a way to apply css to part of the element?

I am looking for a way to apply new CSS to only part of the element.
For example. The original HTML looks like
<p>123456</p>
I want to make only 456 into bold.
Of course, I can do it by adding another tag into 456 like
<p>123<b>456</b></p>
But in my application, I do want not to change the original DOM structure. By adding a new tag, I changed the DOM structure.
To do that, I am thinking of adding new custom attribute to the existing tag like
<p data-wms="e-3">123456</p>
Here data-wms means that there are special part and e-3 means that from index 3 character (it is 4 here) to the end will have a special attribute (like bold in this example)
Now I have all the information about where to change inside the element.
But still, how can I do that with javascript without adding a tag, without changing dom.
Thanks
You can use the span element to do so, it's made specifically to handle inline styling while mantaining the overall structure.
An example would be:
<p>123<span class="bold-highlight">456</span></p>
Thanks to everyone's advice, I researched more, especially about nth-letter.
Though nth-letter is exactly what I want, I found that it is still just proposal, not implemented in any browser.
Thus, there is no way to applying different css letter by letter in one text element without embracing each letter with span tag at this moment (2021-March). I hope that there will be nth-letter in the near future.
I think that I have to re-design my project...
if it's a static page and you want to change a style for specific text in a specific tag like the following case
<p>11111</p>
<p>22222</p>
<p>33333</p>
<p>44444</p>
let's say you want just style the third element, you can change it by the following code using jQuery for sure you can use JavaScript but jQuery will help you to make your code shorter
$( "p:nth-child(3)" ).css("color","#f00");

how to toggle a div on click at different div?

I am trying to toggle a div by clicking on a different div. The only relation that two divs share is that they are inside the same div. I have a DIV class comment which holds DIV class button that is supposed to toggle DIV class box when clicked. The box DIV is also inside the comment DIV. I am trying to use jQuery(this).find(".box").toggle();, but it is not working. I am triggering it with $( ".button" ).click(function(). The script is currently at the bottom of my body.
Could anyone please tell me what am I doing wrong here? I've been playing around with the function for a while now, but with no luck at all. Thank you in advance for your replies.
JSFIDDLE here
HTML
<div class="comment">
<div class="button">
show/hide .box with text1
</div>
<div class="box">
text 1
</div>
</div>
<div class="comment">
<div class="button">
show/hide .box with text2
</div>
<div class="box">
text 2
</div>
<div>
jQuery
$( ".button" ).click(function() {
jQuery(this).find(".box").toggle();
});
You can use the jQuery selector .siblings() to re-write your function like this:
$( ".button" ).click(function() {
$(this).siblings().toggle();
});
Here's a working fiddle to demonstrate.
All you really need to do is this:
$(this).parent().find(".box").toggle();
In short, change:
jQuery(this).find(".box").toggle();
To ONE of the following lines:
$(this).parent('.comment').find(".box").toggle();
$(this).closest('.comment').find(".box").toggle();
$(this).siblings(".box").toggle();
Full Explanation:
The reason it's not working is due to the call. Let's break down your call and see what exactly it's doing.
First we see a simple jQuery selector. This tells jQuery to look for a div containing the class button. Keep in mind, jQuery makes use of any CSS selector. So selecting an item in jQuery is as simple as using it's CSS selector!
$( ".button" )
Next you are assigning an event. In this case, that event is click, meaning you're telling a div having the class button to do something every time it is clicked. Keep in mind, however, not including a callback function is an easy way to trigger this event as well.
$( ".button" ).click(function() {
Now this next line is where your mistake takes place.
jQuery(this).find(".box").toggle();
The first mistake is the use of jQuery. after you're already making use of it's short sign, $. You only need use the elongated name if you are using jQuery's noconflict because another JS library you include might use $. In other words, if $('.button') works and is a jQuery object when used, then you don't need to use jQuery.. See more about this here.
Now, that aside, we can look at jQuery(this) as $(this). Whenever you use $(this) in an Event's callback method, you're referring to the element that the event was tied too. That means that $(this) in your function refers to $('.button'). The problem here is that you then want it to find an inner element containing the class box. Well according to your HTML, that can't happen since .box is a sibling, it is not within the inner HTML of .button. Thus you need to make a different call before you can find .box.
There are actually several solutions here. No solution is more "correct" than another, just simply different and possibly causes a different amount of "time" to run. Now I went with what I saw as being the most simple in that it gives you control over the parent element which contains ALL relevant elements to this function. I'll talk about possible alternatives in a minute.
$(this).closest('.comment')
The above line simply tells .button:clicked to look for the first parent element that contains the class .comment. In other words, this won't find any children or siblings, it will only go up from the current element. This allows us to grab the block that contains all relevant elements and information and thus make maneuvers as needed. So, in the future, you might even use this as a variable in the function, such as:
$('.button').click(function(e) {
var container = $(this).closest('.comment');
Now you can find anything within this element block. In this case you want to find box and toggle it. Thus:
$(this).closest('.comment').find(".box").toggle();
// Or with our variable I showed you
container.find(".box").toggle();
Now, there are plenty of alternatives based on your HTML layout. This example I've given would be good even if .box was buried inside more elements inside .comment, however, given your exact HTML, we see that .button and .box are siblings. This means that you could make this call different entirely and get the same result using something like:
$(this).siblings(".box").toggle();
This will allow our currently clicked and selected button element to look for ANY and ALL siblings having class box. This is a great solution and simple if your HTML is that simple.
However, many times, for "comment" type setups, our HTML is not so simple, nor is it static. It's usually something loaded after the page load. This means our general assignment of .click will not work. Given your exact HTML and not knowing a static Parent ID, I would probably write your code as:
$(document).on('click', '.button', function(e) {
$(this).siblings('.box').toggle();
});
What this does is allow for this click event to be assigned to ANY element containing .button for a class, whether loaded with page or even ten minutes after the page is up. However, the caveat often seen here is the assignment is placed on document. Should we assign a lot of events to document it could become quite convoluted and possibly slow down the client's browser. Not to mention the arguments held over all the other headaches this could cause. So here's my recommendation, make a static (loads with page, is a part of page's main HTML) loading area and do our dynamic assignment to that. For instance:
<div id"Comments"><!-- load comments --></div>
Then you can do the assignment as such:
$('#Comments').on('click', '.button', function(e) {
$(this).siblings('.box').toggle();
});
If you have any more questions, just comment!
Side Note .on is for jQuery versions 1.7+. If using older jQuery, use .live or .bind

How do I style every last element of every line/row differently?

I've been trying to create a grid using
display:inline=block
I need to style every last element of every line/row differently. I tried
nth-child
nth-of-type
However, when I use that, it gets mixed up with my other grids. So how do I do it without adding new classes?
As far as i've seen from your code, you cannot use nth-child to achieve your goal. I will try to explain with an example:
you want the 4th and the 8th child of the section class="four" to be coloured red. In order to use nth-child or nth-of-type, you have to reference to children starting from their parent, i.e. body. So it's difficult to say what number in the list of body's children are the 4th and the 8th children of section class="four", and it's not flexible at all.
I think you are using it in the wrong way, something like section.four:last-child, which is not correct. Please check: w3schools link
Furthermore, nth-child and nth-of-type cannot be used with a selector but only with an element, so no way to do something like .four:nth-child (in the case you make a div with class="four" outside your sections).
So the only way, without adding more classes is jquery, like this:
$('.four').last().css('background-color', 'red');
In CSS3, if you associate every nth-child with a class of some type and every nth-of-type with another class use can style each one differently.
For instance,
<html>
<div class="nth-child">
//some code
</div>
<div class="nth-of-type">
//some code
</div>
</html>
Then in you CSS file you would do something similar to this:
.nth-child
{
//style rules
}
.nth-of-type
{
//style rules
}
I hope this is what you were looking for, without a posted example it is kinda hard to understand what you exactly mean. But if you want to us JS for this then you would create a JS function
obtain all elements in your page using "var elements= document.getElementsByClassName("nth-child")"
the you would loop through "elements.length" setting each element style to "none"

Values of "class" attribute implicitely expand for certain markup elements

I'm experimenting with a third party library written on top of jQuery.
I noticed, for a number of their widgets, that when your source says, for example,
<div id="myWidgetInst" class="their-widget-class-0" ... </div>
Firebug shows that the resulting DOM element reads:
<div id="myWidgetInst" class="their-widget-class-0 their-widget-class-1 ..." ... </div>
How do they do it? Many thanks.
it's probably jquery !
there's probably a function running adding classes to the elements
Not sure I fully understand your question but when looking at the "regular" source of the website, this source doesn't show any modifications to the DOM that happened due to javascript modifications. Firebug does show these updates.
using jQuery, you can add/remove classes simply by using .addClass("className") or .removeClass("className") function on the element you want to modify
They would add classes to the element with jQuery. For example, if the plugin's purpose was to hide all elements on the page (innovative and highly practical, I know), they could use the following:
$(document).ready(function() {
$("*").addClass("my-widget-made-your-element-invisible");
});
With the CSS:
.my-widget-made-your-element-invisible { display: none; }
The methods in which you can manipulate the class attribute in jQuery include the following:
$("#elem").addClass("a"); // adds the class "a" to elem
$("#elem").removeClass("a"); // removes the class "a" from elem
$("#elem").attr("class", "a"); // gives elem a complete class of "a"
$("#elem").attr("class", ""); // removes all classes from attribute

How to implement unobtrusive javascript with dynamic content generation?

I write a lot of dynamically generated content (developing under PHP) and I use jQuery to add extra flexibility and functionality to my projects.
Thing is that it's rather hard to add JavaScript in an unobtrusive manner. Here's an example:
You have to generate a random number of div elements each with different functionality triggered onClick. I can use the onclick attribute on my div elements to call a JS function with a parameter but that is just a bad solution. Also I could generate some jQuery code along with each div in my PHP for loop, but then again this won't be entirely unobtrusive.
So what's the solution in situations like this?
You need to add something to the divs that defines what type of behaviour they have, then use jQuery to select those divs and add the behaviour. One option is to use the class attribute, although arguably this should be used for presentation rather than behaviour. An alternative would be the rel attribute, but I usually find that you also want to specify different CSS for each behaviour, so class is probably ok in this instance.
So for instance, lets assume you want odd and even behaviour:
<div class="odd">...</div>
<div class="even">...</div>
<div class="odd">...</div>
<div class="even">...</div>
Then in jQuery:
$(document).load(function() {
$('.odd').click(function(el) {
// do stuff
});
$('.even').click(function(el) {
// dostuff
});
});
jQuery has a very powerful selector engine that can find based on any CSS based selector, and also support some XPath and its own selectors. Get to know them! http://docs.jquery.com/Selectors
I would recommend that you use this thing called "Event delegation". This is how it works.
So, if you want to update an area, say a div, and you want to handle events unobtrusively, you attach an event handler to the div itself. Use any framework you prefer to do this. The event attachment can happen at any time, regardless of if you've updated the div or not.
The event handler attached to this div will receive the event object as one of it's arguments. Using this event object, you can then figure which element triggered the event. You could update the div any number of times: events generated by the children of the div will bubble up to the div where you can catch and handle them.
This also turns out to be a huge performance optimization if you are thinking about attaching multiple handlers to many elements inside the div.
I would recommend disregarding the W3C standards and writing out HTML-properties on the elements that need handlers attached to them:
Note: this will not break the rendering of the page!
<ul>
<li handler="doAlertOne"></li>
<li handler="doAlertTwo"></li>
<li handler="doAlertThree"></li>
</ul>
Declare a few functions:
function doAlertOne() { }
function doAlertTwo() { }
function doAlertThree() { }
And then using jQuery like so:
$("ul li").each(function ()
{
switch($(this).attr("handler"))
{
case "doAlertOne":
doAlertOne();
break;
case ... etc.
}
});
Be pragmatic.
It's a bit hard to tell from your question, but perhaps you can use different jQuery selectors to set up different click behaviours? For example, say you have the following:
<div class="section-1">
<div></div>
</div>
<div class="section-2">
<div></div>
</div>
Perhaps you could do the following in jQuery:
$('.section-1 div').onclick(...one set of functionality...);
$('.section-2 div').onclick(...another set of functionality...);
Basically, decide based on context what needs to happen. You could also select all of the divs and test for some parent or child element to determine what functionality they get.
I'd have to know more about the specifics of your situation to give more focused advice, but maybe this will get you started.
I haven't don't really know about JQuery, but I do know that the DOJO toolkit does make highly unobtrusive Javascript possible.
Take a look at the example here: http://dojocampus.org/explorer/#Dojo_Query_Adding%20Events
The demo dynamically adds events to a purely html table based on classes.
Another example is the behaviour features, described here:http://dojocampus.org/content/2008/03/26/cleaning-your-markup-with-dojobehavior/

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