Answers for "create element by class name"

javascript element by class

var elementsArray = document.getElementsByClassName("someclassname");

get element by class

var elements = document.getElementsByClassName(names); // or:
var elements = rootElement.getElementsByClassName(names);

js create element with class

var element =document.createElement("span");
        element.className = "aClassName";

Finding HTML Elements by Class Name

const x = document.getElementsByClassName("intro");