#myElement *, #myElement *:before {
   outline:1px dotted red;
}

var myCSS = "#myElement *, #myElement *:before {outline:1px dotted red;}";
// document.addCSS(myCSS);

myStyle.insertRule("#blanc { color: white }", 0);

#myElement.outline *, #myElement.outline *:before {
  outline:1px dotted red;
}

document.getElementById("myElement").className += " MyClass";

document.getElementById("myElement").classList.add('newclass');

 document.getElementById("myElement").classList.remove('newclass');

body.outline #myElement *

document.body.classList.toggle('outline');

#myElement.outline *

IF (element matches selector) THEN apply rule;

#myElement.outline

body.outline #myElement *
            ^          ^

.outline, .active

#myElement.outline { outline: dotted red 1px; }
#myElement.outline.active { outline: solid blue 10px; }

var sheet = document.styleSheets[0];
sheet.insertRule(".foo { color:pink; }", sheet.cssRules.length);

sheet.addRule(".foo", "color: pink;", -1);