.container
  p.value RETURN VALUE
  span.target#target TARGET ELEMENT
  .btns
    button(type='button' data-method='getElementById') getElementById
    button(type='button' data-method='getElementsByClassName') getElementsByClassName
    button(type='button' data-method='getElementsByTagName') getElementsByTagName
    button(type='button' data-method='querySelector') querySelector
    button(type='button' data-method='querySelectorAll') querySelectorAll

@import url('https://fonts.googleapis.com/css?family=Dosis:500&display=swap');
* {
  font-family: 'Dosis', sans-serif;
  letter-spacing: .1rem;
}
body {
  display: flex;
  justify-content: center;
  align-items: center;
  text-align: center;
  background-color: #212121;
  height: 100vh;
}
p {
  margin: 0;
}
em {
  color: #f00;
}
button {
  flex-grow: 1;
  font-size: 1rem;
  padding: .8rem 1rem;
  margin: .2rem;
  background: #FFC107;
  border: none;
  font-weight: bold;
  cursor: pointer;
  border-radius: .2rem;
  transition: background-color .3s;
  &:hover {
    background-color: #ffe082;
  }
}
.target {
  display: block;
  margin: 3rem;
  text-align: center;
  font-size: 1.6rem;
  font-weight: bold;
  color: #fff;
}
.value {
  display: inline-block;
  padding: 1rem 2rem;
  margin-bottom: .4rem;
  border-radius: .4rem;
  background-color: #fff;
}
.btns {
  display: flex;
  flex-wrap: wrap;
  max-width: 700px;
}

const btns = document.querySelectorAll('button');
const value = document.querySelector('.value');
let target;
btns.forEach( btn => {
  btn.addEventListener('click', e => {
    switch(e.target.dataset.method) {
      case 'getElementById' :
        target = document.getElementById('target');
        break;
      case 'getElementsByClassName' :
        target = document.getElementsByClassName('target');
        break;
      case 'getElementsByTagName' :
        target = document.getElementsByTagName('span');
        break;
      case 'querySelector' :
        target = document.querySelector('span');
        break;
      case 'querySelectorAll' :
        target = document.querySelectorAll('span');
        break;
    }
    if(!target.outerHTML){
      value.innerHTML = `<b>${target}</b> = <em>like Array(But not Array).</em>`;
      value.style.background = '#FFECB4'
    } else {
      value.innerText = target.outerHTML;
      value.style.background = ''
    }
  });
});