v4.1

jQuery4.js

function $(container, selector) {
  const els =
    typeof selector === 'string'
      ? container.querySelectorAll(selector)
      : typeof container === 'string' ? document.querySelectorAll(container) : [container];

  const fns = {
    removeClass(...cls) {
      els.forEach(el => {
        el.classList.remove(...cls);
      });
      return this;
    },
    addClass(...cls) {
      els.forEach(el => {
        el.classList.add(...cls);
      });
      return this;
    },
    toggleClass(cls, b) {
      els.forEach(el => {
        el.classList.toggle(cls, b);
      });
      return this;
    },
    on(type, cb, opts) {
      els.forEach(el => {
        el.addEventListener(type, cb, opts);
      });
      return this;
    },
    off(type, cb, opts) {
      els.forEach(el => {
        el.removeEventListener(type, cb, opts);
      });
      return this;
    },
    css(props) {
      els.forEach(el => {
        Object.assign(el.style, props);
      });
      return this;
    },
  };
  return new Proxy(els, {
    get(targ, k) {
      return els[k] || fns[k];
    },
  });
}