anchor.diff:  
     const tagTrafficLightHtml = (tagNumber) => {
       const index = indexForTag(tagNumber);
  -    const colour = (index == null) ? '' : param.tags[index].colour;
  +    const colour = (index === null) ? '' : param.tags[index].colour;
       return `<div id="tag-number" class="${colour}">${tagNumber}</div>`;
     };
   
     // - - - - - - - - - - - - - - - - - - - - - - - -
   
     const refreshTag = (button, newTag) => {
  -    const on = newTag != null;
  +    const on = newTag !== null;
       button
         .attr('disabled', !on)
         .css('cursor', on ? 'pointer' : 'default');
       if (on) {
         button
           .unbind('click')
  -        .bind('click', () => { show(newTag); });
  +        .bind('click', () => show(newTag));
       }
     };
   
  
positive.code:     // For some reason the hover-tip gets displayed behind
      // the file-diff.
      html += '<td>';
      html += "<div class='traffic-light-count " + lastColour + "'>";
      html += trafficLightCount;
      html += '</div>';
      html += '</td>';
  
negative.code: 
    const getNextTag = () => {
      const index = indexForTag(param.nowTag);
      if (index === null || index === param.tags.length - 1)
        return null;
      else
        return param.tags[index + 1].index;
  