little pretend jQuery

myjQuery.js

function $(selector) {

  function selectWithJS() {
    let selectorType = selector.split('').shift();
    let selectorName = selector.substr(1);
    if (selectorType === '#') {
      return document.getElementById(selectorName);
    } else {
      return document.querySelectorAll(selectorName);
    }
  }

  return {
    addClass(className) {
      if (selector.includes('#')) {
        document.getElementById('foo').classList.add(className);
      } else {
        document.querySelectorAll('foo').classList.add(className);
      }
    }
  }

}