How to scale element in pixel with CSS? [duplicate]

Question

Elements can be scaled with transform: scale(sx), where sx is the (unit-less) scale factor. Is there some way to scale an element down by a certain number of pixel (without knowing its width).

Edit

I would like to resize elements of different sizes, like buttons, down when they are pressed. However, applying the same scale factor, say scale(.95), on all buttons leads to the bigger (smaller) ones to be scaled too much (little). So, what I would like to do is resize all elements when pressed absolutely, i.e. by a certain number of pixel or em or so.

Answer 1

This is how you could scale the width using vanilla JavaScript

const reduction=10;//in pixels
let button = document.querySelector("#myButton");
button.addEventListener("click",(event)=>{
  let style=window.getComputedStyle(button);
  let realWidth=parseInt(style.width);
  console.log(realWidth);
  let newWidth=realWidth-reduction;//some redundancy here
  button.style.width=`${newWidth}px`;//this changes the actual width property. With jQuery it would be even easier.
},false);

#myButton{
width:300px;
height:50px;
}

<button id="myButton">Click here to resize</button>

Answer 2

The only way I would know (with css only) is if you do the following:

This only works as long as it's width and height are not dependent on the elements content

1. Surround the element you want to scale with an element that represents the default size. This can either be set in pixels or as a percentage or whatever scale it choses (like auto)
2. On :hover use the css calc function to do calc(100% - <number><em|rm|px|%>) to scale it by any value and unit available in css.

<div class="button-size">
    <button>
        Hover me please
    </button>
</div>

.button-size
{
    width: 300px;
    height: 450px;
}
.button-size button
{
    width: 100%;
    height: 100%;
    margin: 8px;
}
.button-size button
{
    transition: all ease-in-out .5s; /* easy animation if you need it */
}
.button-size button:hover
{
    width: calc(100% - 20px);
    height: calc(100% - 3em);
}