How to add property to existing class

Question

I have got a CSS class like so:

.simpleClass {
    width: 25px;
}

And I have a matching element:

Answer 1

If I get it right, You don't want to give property to the instance element of simpleClass, but would like to give an extra property to the whole class ( covering all instances ) using JS.

In this case, You can use jQuery to append a style element to the head, giving You the opportunity to add additional CSS declarations.

However, I would not recommend this, because it causes Your code, and structure to get messy.

$("head").append("");

This snippet will give extra display:none property to all .simpleClass elements existing in the time of doing this, and will also affect every later-inserted .simpleClass elements.