Answers for "create new class name from javascdritp"

js add class

var element = document.getElementById('element');
element.classList.add('class-1');
element.classList.add('class-2', 'class-3');
element.classList.remove('class-3');

create element javascript with class

// create div element by javascript with class

var div = document.createElement('div');
div.className = "div1";

none

// create div element by javascript with class

var div = document.createElement('div');
div.className = "div1";