What's wrong with my auto-underline script?

Question

I want to use Tobias Ahlin's script to style up my input-box. But while it's perfectly working on paragraphs, on inputs doesn't. Also, the ::before doesn't show up in the spectator.

Here's my code:

.edit input {
    text-decoration: none;
    outline: none;
    border: none;
    position: relative;
    font-size: 1.125rem;
}

.edit input::before {
    content: "";
    position: absolute;
    width: 100%;
    height: 2px;
    bottom: 0;
    left: 0;
    background-color: #000;
    visibility: hidden;
    transform: scaleX(0);
    transition: all 0.15s ease-in-out 0s;
}
.edit input:active::before, .edit input:focus::before {
    visibility: visible;
    transform: scaleX(1);
}

<div class="edit">
  <input type="text" maxlength="15" value="Some content here...">
</div>

I'm using it in an Angular 5 application, but I don't think it's relevant right now.

Answer 1

The problem is that input and other form elements don't render :before and :after pseudo elements.

Authors specify the style and location of generated content with the :before and :after pseudo-elements. As their names indicate, the :before and :after pseudo-elements specify the location of content before and after an element's document tree content. The 'content' property, in conjunction with these pseudo-elements, specifies what is inserted.

W3 Specs

So wrapping the input in a span would make this to work:

<div class="edit">
  <span><input type="text" maxlength="15" value="Some content here..."></span>
</div>

CSS ... please note for .edit span::before bottom: -2px difference than your code.

span {
  position: relative;
}

.edit input {
    text-decoration: none;
    outline: none;
    border: none;
    position: relative;
    font-size: 1.125rem;
}

.edit span::before {
    content: "";
    position: absolute;
    width: 100%;
    height: 2px;
    bottom: -2px;
    left: 0;
    background-color: #000;
    visibility: hidden;
    transform: scaleX(0);
    transition: all 0.15s ease-in-out 0s;
}
.edit span:hover::before {
    visibility: visible;
    transform: scaleX(1);
}