code: function(avoidHiddenFields) {
        var field,
            fieldName,
            newValue,
            focusedElement = document.querySelector(":focus"),
            fields         = this.container.querySelectorAll(SELECTOR_FIELDS),
            length         = fields.length,
            i              = 0;
        for (; i<length; i++) {
          field = fields[i];
          
          // Never change elements where the user is currently typing in
          if (field === focusedElement) {
            continue;
          }
          
          // Don't update hidden fields
          // See https://github.com/xing/wysihtml5/pull/14
          if (avoidHiddenFields && field.type === "hidden") {
            continue;
          }
          
          fieldName = field.getAttribute(ATTRIBUTE_FIELDS);
          newValue  = this.elementToChange ? (this.elementToChange[fieldName] || "") : field.defaultValue;
          field.value = newValue;
        }
      }
docs: Takes the attributes of the "elementToChange"
  and inserts them in their corresponding dialog input fields
  
  Assume the "elementToChange" looks like this:
  <a href="http://www.google.com" target="_blank">foo</a>
  
  and we have the following dialog:
  <input type="text" data-wysihtml5-dialog-field="href" value="">
  <input type="text" data-wysihtml5-dialog-field="target" value="">
  
  after calling _interpolate() the dialog will look like this
  <input type="text" data-wysihtml5-dialog-field="href" value="http://www.google.com">
  <input type="text" data-wysihtml5-dialog-field="target" value="_blank">
  
  Basically it adopted the attribute values into the corresponding input fields