anchor.diff:  $(() => {
   
     const review = cd.review;
  +
  +  const $trafficLights = $('#review-traffic-lights');
   
     review.refreshTrafficLights = (params) => {
       const args = { id:params.id };
  
positive.code:   };
  
    // - - - - - - - - - - - - - - - - - - - - - - - -
    const makeTrafficLightsHtml = (events) => {
      let html = '';
      events.forEach((event,number) => {
        if (isVisible(event)) {
          html += makeTrafficLightHtml(event, number);
        }
      });
      return html;
    };
  
    // - - - - - - - - - - - - - - - - - - - - - - - -
  
negative.code:   };
  
    // - - - - - - - - - - - - - - - - - - - - - - - -
    const wasPredicted = (light) => light.predicted != undefined && light.predicted != 'none';
    const wasReverted = (light) => light.revert != undefined;
  
    // - - - - - - - - - - - - - - - - - - - - - - - -
    const appendPredictedMarker = (light) => {
      const correct = (light.predicted === light.colour);
      const icon = correct ? 'tick' : 'cross';
      const $predicted = $('<img>', {
        class: icon,
          src: `/images/traffic-light/circle-${icon}.png`
      });
      $trafficLights.append($predicted);
    };
  
    const appendRevertedMarker = (light) => {
      const $revert = $('<img>', {
        class: 'revert',
          src: '/images/traffic-light/circle-revert.png'
      });
      $trafficLights.append($revert);
    };
  
    // - - - - - - - - - - - - - - - - - - - - - - - -
    const appendTrafficLight = (light, number) => {
      const $light = $('<div>', {
           id: review.params.id,
        class: 'diff-traffic-light',
        'data-number': number,
        'data-colour': light.colour,
        'data-index': light.index
      });
      const $img = $('<img>', { src: `/images/traffic-light/${light.colour}.png` });
      $light.append($img);
      $light.append(makeTrafficLightMarkerHtml(light));
      $trafficLights.append($light);
    };
  
    // - - - - - - - - - - - - - - - - - - - - - - - -
    const makeTrafficLightMarkerHtml = (light) => {
      const isCurrentIndex = (review.params.nowIndex === light.index);
      if (isCurrentIndex) {
        return `<img id='traffic-light-marker'
                     src='/images/traffic-light/marker_${light.colour}.png'/>`;
      } else {
  