If we're using ES2015, why not save a byte?

  <script>(o=b=>{for(j in a)for(i in a)y=a[i]+-~j,b?document.write([["<p>"][i]]+`<input onfocus=value=[o[id]] onblur=o[id]=value;o() id=${y}>`):eval(y+(".value"+o[y]).replace(/[A-Z]\d/g," +$&.value"))})(a="ABCD")</script>