$(el).toggleClass(className);

if (el.classList) {
  el.classList.toggle(className);
} else {
  var classes = el.className.split(" ");
  var existingIndex = classes.indexOf(className);

  if (existingIndex >= 0) classes.splice(existingIndex, 1);
  else classes.push(className);

  el.className = classes.join(" ");
}

const toggleClass = require("class-toggle");
toggleClass(el, className);

el.classList.toggle(className);

const toggleClass = require("class-toggle");

const div = document.createElement("div");
div.outerHTML;
//=> '<div></div>'

toggleClass(div, "my-class");

div.outerHTML;
//=> '<div class="my-class"></div>'

toggleClass(div, "other-class");

div.outerHTML;
//=> '<div class="my-class other-class"></div>'

toggleClass(div, "my-class");

div.outerHTML;
//=> '<div class="other-class"></div>'