Вариант миграции с JQuery на чистый Javascript

Я не понимаю, о чем вы говорите.

Про циклы говорит:

$('.foobar').addClass('bla')

или

Array.from(document.getElementsByClassName("foobar")).forEach(el => {
    el.classList.add('bla');
});

Object.prototype.find = function(s){return this.querySelectorAll(s);}
Object.prototype.bind = function(cssSelectors,events,callback,debug=false){
  events = events.split(',');
  elements= this.find(cssSelectors)||this;
  elements.forEach(element=>{
    events.forEach(event=>{
      element.addEventListener(event,callback);
      if (debug) console.dir(element+' listen '+event);
    });
  });
}
document.bind('a,p','click,mouseup',(e)=>{});

Object.prototype.on = function(f,c){return Array.from(this,(i)=>i.addEventListener(f,c));}
Object.prototype.find = function(s){return this.querySelectorAll(s);}
Object.prototype.first = function(s){if(!s) return this.firstElementChild;return this.querySelector(s);}
Object.prototype.next = function(){return this.nextElementSibling;};
Object.prototype.prev = function(){return this.previousElementSibling;};
Object.prototype.last = function(){return this.lastElementChild;};
Object.prototype.parents = function(cssSelectors){
  if(!cssSelectors) return this.parentElement;
    cssSelectors = cssSelectors.split(',');
    const a=[];
    for(let i=0;i<=cssSelectors.length;i++) {
      var p=this.parentElement;
      while(p){
        if (p.matches(cssSelectors[i])) {a.push(p);}
        p=p.parentElement;
      }
  }
  return a;
};