Function groupAnimations

test/angular/1.5/angular-animate.js:3099–3180

(animations)

      }

      function groupAnimations(animations) {
        var preparedAnimations = [];
        var refLookup = {};
        forEach(animations, function(animation, index) {
          var element = animation.element;
          var node = getDomNode(element);
          var event = animation.event;
          var enterOrMove = ['enter', 'move'].indexOf(event) >= 0;
          var anchorNodes = animation.structural ? getAnchorNodes(node) : [];

          if (anchorNodes.length) {
            var direction = enterOrMove ? 'to' : 'from';

            forEach(anchorNodes, function(anchor) {
              var key = anchor.getAttribute(NG_ANIMATE_REF_ATTR);
              refLookup[key] = refLookup[key] || {};
              refLookup[key][direction] = {
                animationID: index,
                element: jqLite(anchor)
              };
            });
          } else {
            preparedAnimations.push(animation);
          }
        });

        var usedIndicesLookup = {};
        var anchorGroups = {};
        forEach(refLookup, function(operations, key) {
          var from = operations.from;
          var to = operations.to;

          if (!from || !to) {
            // only one of these is set therefore we can't have an
            // anchor animation since all three pieces are required
            var index = from ? from.animationID : to.animationID;
            var indexKey = index.toString();
            if (!usedIndicesLookup[indexKey]) {
              usedIndicesLookup[indexKey] = true;
              preparedAnimations.push(animations[index]);
            }
            return;
          }

          var fromAnimation = animations[from.animationID];
          var toAnimation = animations[to.animationID];
          var lookupKey = from.animationID.toString();
          if (!anchorGroups[lookupKey]) {
            var group = anchorGroups[lookupKey] = {
              structural: true,
              beforeStart: function() {
                fromAnimation.beforeStart();
                toAnimation.beforeStart();
              },
              close: function() {
                fromAnimation.close();
                toAnimation.close();
              },