micro-in-place-editor.html

<div id="myElement">asdfa</div>

<script>
var element = document.querySelector('#myElement')
element.addEventListener('dblclick', makeEditable, false)

function makeEditable(e) {
  var editable = e.target,
      input = document.createElement('input')
  input.value = editable.textContent
  editable.innerHTML = ''
  editable.appendChild(input)
  input.focus()
  input.addEventListener('blur', function(e) {
    editable.innerHTML = input.value
  }, false)
}
</script>