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    %a(href="" data-isbn="978-4-7741-4223-4") Apache ポケットリファレンス
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  %input#delete(type="button" value="Delete" disabled="disabled")




                body { padding: 1rem; }
div { padding: 1rem; }


                'use strict'

const list = document.getElementById('show');
list.addEventListener('click', show, false);

const delBtn = document.getElementById('delete');
delBtn.addEventListener('click', del, false);

function show(event) {
  let target =;
  let isbn = target.dataset.isbn;

  let img = document.createElement('img');
  img.src = `//${isbn}/${isbn}.jpg`;
  img.alt = target.textContent;
  img.height = 150;
  img.width = 108;

  let pic = document.getElementById('pic');
  if (pic.getElementsByTagName('img').length > 0) {
    pic.replaceChild(img, pic.lastChild);
  } else {
    document.getElementById('delete').disabled = false;


function del() {
  let pic = document.getElementById('pic');
  document.getElementById('delete').disabled = true;