Selecting and manipulating CSS pseudo-elements suc

Question

Is there any way to select/manipulate CSS pseudo-elements such as ::before and ::after (and the old version with one semi-colon) using jQuery?

For example, my stylesheet has the following rule:

.span::after{ content:'foo' }

How can I change 'foo' to 'bar' using jQuery?

Answer 1

IF you want to to manipulate the ::before or ::after sudo elements entirely through CSS, you could do it JS. See below;

jQuery('head').append('<style id="mystyle" type="text/css"> /* your styles here */ </style>');

Notice how the <style> element has an ID, which you can use to remove it and append to it again if your style changes dynamically.

This way, your element is style exactly how you want it through CSS, with the help of JS.

Answer 2

Here is the HTML:

<div class="icon">
  <span class="play">
    ::before
  </span>
</div>

Computed style on 'before' was content: "VERIFY TO WATCH";

Here is my two lines of jQuery, which use the idea of adding an extra class to specifically reference this element and then appending a style tag (with an !important tag) to changes the CSS of the sudo-element's content value:

$("span.play:eq(0)").addClass('G');

$('body').append("<style>.G:before{content:'NewText' !important}</style>");

Answer 3

You'd think this would be a simple question to answer, with everything else that jQuery can do. Unfortunately, the problem comes down to a technical issue: css :after and :before rules aren't part of the DOM, and therefore can't be altered using jQuery's DOM methods.

There are ways to manipulate these elements using JavaScript and/or CSS workarounds; which one you use depends on your exact requirements.

---

I'm going to start with what's widely considered the "best" approach:

1) Add/remove a predetermined class

In this approach, you've already created a class in your CSS with a different :after or :before style. Place this "new" class later in your stylesheet to make sure it overrides:

p:before {
    content: "foo";
}
p.special:before {
    content: "bar";
}

Then you can easily add or remove this class using jQuery (or vanilla JavaScript):

$('p').on('click', function() {
    $(this).toggleClass('special');
});

    $('p').on('click', function() {
      $(this).toggleClass('special');
    });

p:before {
  content: "foo";
  color: red;
  cursor: pointer;
}
p.special:before {
  content: "bar";
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

<p>This is a paragraph.</p>
<p>This is another paragraph.</p>

• Pros: Easy to implement with jQuery; quickly alters multiple styles at once; enforces separation of concerns (isolating your CSS and JS from your HTML)
• Cons: CSS must be pre-written, so the content of :before or :after isn't completely dynamic

---

2) Add new styles directly to the document's stylesheet

It's possible to use JavaScript to add styles directly to the document stylesheet, including :after and :before styles. jQuery doesn't provide a convenient shortcut, but fortunately the JS isn't that complicated:

var str = "bar";
document.styleSheets[0].addRule('p.special:before','content: "'+str+'";');

var str = "bar";
document.styleSheets[0].addRule('p.special:before', 'content: "' + str + '";');

p:before {
  content: "foo";
  color: red;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

<p class="special">This is a paragraph</p>
<p>This is another paragraph</p>

.addRule() and the related .insertRule() methods are fairly well-supported today.

As a variation, you can also use jQuery to add an entirely new stylesheet to the document, but the necessary code isn't any cleaner:

var str = "bar";
$('<style>p.special:before{content:"'+str+'"}</style>').appendTo('head');

var str = "bar";
$('<style>p.special:before{content:"' + str + '"}</style>').appendTo('head');

p:before {
  content: "foo";
  color: red;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

<p class="special">This is a paragraph</p>
<p>This is another paragraph</p>

If we're talking about "manipulating" the values, not just adding to them, we can also read the existing :after or :before styles using a different approach:

var str = window.getComputedStyle(document.querySelector('p'), ':before') 
           .getPropertyValue('content');

var str = window.getComputedStyle($('p')[0], ':before').getPropertyValue('content');
console.log(str);

document.styleSheets[0].addRule('p.special:before', 'content: "' + str+str + '";');

p:before {
    content:"foo";
    color: red;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

<p class="special">This is a paragraph</p>
<p>This is another paragraph</p>

We can replace document.querySelector('p') with $('p')[0] when using jQuery, for slightly shorter code.

• Pros: any string can be dynamically inserted into the style
• Cons: original styles aren't altered, just overridden; repeated (ab)use can make the DOM grow arbitrarily large

---

3) Alter a different DOM attribute

You can also to use attr() in your CSS to read a particular DOM attribute. (If a browser supports :before, it supports attr() as well.) By combining this with content: in some carefully-prepared CSS, we can change the content (but not other properties, like margin or color) of :before and :after dynamically:

p:before {
    content: attr(data-before);
    color: red;
    cursor: pointer;
}

JS:

$('p').on('click', function () {
    $(this).attr('data-before','bar');
});

$('p').on('click', function () {
    $(this).attr('data-before','bar');
});

p:before {
    content: attr(data-before);
    color: red;
    cursor: pointer;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

<p>This is a paragraph.</p>
<p>This is another paragraph.</p>

This can be combined with the second technique if the CSS can't be prepared ahead of time:

var str = "bar";

document.styleSheets[0].addRule('p:before', 'content: attr(data-before);');

$('p').on('click', function () {
    $(this).attr('data-before', str);
});

var str = "bar";
document.styleSheets[0].addRule('p:before', 'content: attr(data-before) !important;');

$('p').on('click', function() {
  $(this).attr('data-before', str);
});

p:before {
  content: "foo";
  color: red;
  cursor: pointer;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

<p>This is a paragraph.</p>
<p>This is another paragraph.</p>

• Pros: Doesn't create endless extra styles
• Cons: attr in CSS can only apply to content strings, not URLs or RGB colors

Answer 4

This is not practical as i did not write this for real world uses, just to give you a example of what can be achieved.

css = {
before: function(elem,attr){ 

if($("#cust_style") !== undefined){ 
$("body").append("<style> " + elem + ":before {"  + attr +  "} </style>"); 
} else {
 $("#cust_style").remove();
$("body").append("<style> " + elem + ":before {"  + attr +  "} </style>"); 
}

}, after: function(elem,attr){
if($("#cust_style") !== undefined){ 
$("body").append("<style> " + elem + ":after {"  + attr +  "} </style>"); 

} else { $("#cust_style").remove();
$("body").append("<style> " + elem + ":after {"  + attr +  "} </style>"); 
}
}
}

this currently add's a / or appends a Style element which contains your necessary attribute's which will take affect on the target element's after Pseudo element.

this can be used as

css.after("someElement"," content: 'Test'; position: 'absolute'; ") // editing / adding styles to :after

and

css.before( ... ); // to affect the before pseudo element.

as after: and before: pseudo elements are not directly accessible through DOM it is currently not possible to edit the Specific values of the css freely.

my way was just a example and its not good for practice, you can modify it try some of your own tricks and make it correct for real world usage.

so do your own experimentation's with this and others!

regards - Adarsh Hegde.

Answer 5

I made use of variables defined in :root inside CSS to modify the :after (the same applies to :before) pseudo-element, in particular to change the background-color value for a styled anchor defined by .sliding-middle-out:hover:after and the content value for another anchor (#reference) in the following demo that generates random colors by using JavaScript/jQuery:

HTML

<a href="#" id="changeColor" class="sliding-middle-out" title="Generate a random color">Change link color</a>
<span id="log"></span>
<h6>
  <a href="https://stackoverflow.com/a/52360188/2149425" id="reference" class="sliding-middle-out" target="_blank" title="Stack Overflow topic">Reference</a>
</h6>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script type="text/javascript" src="https://cdn.rawgit.com/davidmerfield/randomColor/master/randomColor.js"></script>

CSS

:root {
    --anchorsFg: #0DAFA4;
}
a, a:visited, a:focus, a:active {
    text-decoration: none;
    color: var(--anchorsFg);
    outline: 0;
    font-style: italic;

    -webkit-transition: color 250ms ease-in-out;
    -moz-transition: color 250ms ease-in-out;
    -ms-transition: color 250ms ease-in-out;
    -o-transition: color 250ms ease-in-out;
    transition: color 250ms ease-in-out;
}
.sliding-middle-out {
    display: inline-block;
    position: relative;
    padding-bottom: 1px;
}
.sliding-middle-out:after {
    content: '';
    display: block;
    margin: auto;
    height: 1px;
    width: 0px;
    background-color: transparent;

    -webkit-transition: width 250ms ease-in-out, background-color 250ms ease-in-out;
    -moz-transition: width 250ms ease-in-out, background-color 250ms ease-in-out;
    -ms-transition: width 250ms ease-in-out, background-color 250ms ease-in-out;
    -o-transition: width 250ms ease-in-out, background-color 250ms ease-in-out;
    transition: width 250ms ease-in-out, background-color 250ms ease-in-out;
}
.sliding-middle-out:hover:after {
    width: 100%;
    background-color: var(--anchorsFg);
    outline: 0;
}
#reference {
  margin-top: 20px;
}
.sliding-middle-out:before {
  content: attr(data-content);
  display: attr(data-display);
}

JS/jQuery

var anchorsFg = randomColor();
$( ".sliding-middle-out" ).hover(function(){
    $( ":root" ).css({"--anchorsFg" : anchorsFg});
});

$( "#reference" ).hover(
 function(){
    $(this).attr("data-content", "Hello World!").attr("data-display", "block").html("");
 },
 function(){
    $(this).attr("data-content", "Reference").attr("data-display", "inline").html("");
 }
);

Answer 6

You can't select pseudo elements in jQuery because they are not part of DOM. But you can add an specific class to the father element and control its pseudo elements in CSS.

EXAMPLE

In jQuery:

<script type="text/javascript">
    $('span').addClass('change');
</script>

In CSS:

span.change:after { content: 'bar' }