perf($rootScope): make postDigestQueue more efficient

Author: thorn0

src/ng/rootScope.js

@@ -848,7 +848,7 @@ function $RootScopeProvider() {
 
         clearPhase();
 
-        while (postDigestQueue.length) {
+        while (!postDigestQueue.isEmpty()) {
           try {
             postDigestQueue.shift()();
           } catch (e) {
@@ -1306,7 +1306,7 @@ function $RootScopeProvider() {
 
     //The internal queues. Expose them on the $rootScope for debugging/testing purposes.
     var asyncQueue = $rootScope.$$asyncQueue = [];
-    var postDigestQueue = $rootScope.$$postDigestQueue = [];
+    var postDigestQueue = $rootScope.$$postDigestQueue = new Queue();
     var applyAsyncQueue = $rootScope.$$applyAsyncQueue = [];
 
     return $rootScope;
@@ -1364,5 +1364,26 @@ function $RootScopeProvider() {
         });
       }
     }
+
+    // See https://github.com/angular/angular.js/issues/14534
+    function Queue() {
+      var array = [],
+          head = 0;
+      this.push = function(item) {
+        array.push(item);
+      };
+      this.shift = function() {
+        var item = array[head];
+        array[head] = null;
+        if (++head > 100 && head * 2 >= array.length) {
+          array = array.slice(head);
+          head = 0;
+        }
+        return item;
+      };
+      this.isEmpty = function() {
+        return head === array.length;
+      };
+    }
   }];
 }

test/ng/rootScopeSpec.js

@@ -1320,46 +1320,6 @@ describe('Scope', function() {
       expect(externalWatchCount).toEqual(0);
     }));
 
-    it('should run a $$postDigest call on all child scopes when a parent scope is digested', inject(function($rootScope) {
-      var parent = $rootScope.$new(),
-          child = parent.$new(),
-          count = 0;
-
-      $rootScope.$$postDigest(function() {
-        count++;
-      });
-
-      parent.$$postDigest(function() {
-        count++;
-      });
-
-      child.$$postDigest(function() {
-        count++;
-      });
-
-      expect(count).toBe(0);
-      $rootScope.$digest();
-      expect(count).toBe(3);
-    }));
-
-    it('should run a $$postDigest call even if the child scope is isolated', inject(function($rootScope) {
-      var parent = $rootScope.$new(),
-          child = parent.$new(true),
-          signature = '';
-
-      parent.$$postDigest(function() {
-        signature += 'A';
-      });
-
-      child.$$postDigest(function() {
-        signature += 'B';
-      });
-
-      expect(signature).toBe('');
-      $rootScope.$digest();
-      expect(signature).toBe('AB');
-    }));
-
     it('should cause a $digest rerun', inject(function($rootScope) {
       $rootScope.log = '';
       $rootScope.value = 0;
@@ -1705,6 +1665,93 @@ describe('Scope', function() {
     }));
   });
 
+  describe('$$postDigest', function() {
+    it('should process callbacks as a queue (FIFO) when the scope is digested', inject(function($rootScope) {
+      var signature = '';
+
+      $rootScope.$$postDigest(function() {
+        signature += 'A';
+        $rootScope.$$postDigest(function() {
+          signature += 'D';
+        });
+      });
+
+      $rootScope.$$postDigest(function() {
+        signature += 'B';
+      });
+
+      $rootScope.$$postDigest(function() {
+        signature += 'C';
+      });
+
+      expect(signature).toBe('');
+      $rootScope.$digest();
+      expect(signature).toBe('ABCD');
+    }));
+
+    it('should support $apply calls nested in $$postDigest callbacks', inject(function($rootScope) {
+      var signature = '';
+
+      $rootScope.$$postDigest(function() {
+        signature += 'A';
+      });
+
+      $rootScope.$$postDigest(function() {
+        signature += 'B';
+        $rootScope.$apply();
+        expect($rootScope.$$postDigestQueue.isEmpty()).toBe(true);
+        signature += 'D';
+      });
+
+      $rootScope.$$postDigest(function() {
+        signature += 'C';
+      });
+
+      expect(signature).toBe('');
+      $rootScope.$digest();
+      expect(signature).toBe('ABCD');
+    }));
+
+    it('should run a $$postDigest call on all child scopes when a parent scope is digested', inject(function($rootScope) {
+      var parent = $rootScope.$new(),
+          child = parent.$new(),
+          count = 0;
+
+      $rootScope.$$postDigest(function() {
+        count++;
+      });
+
+      parent.$$postDigest(function() {
+        count++;
+      });
+
+      child.$$postDigest(function() {
+        count++;
+      });
+
+      expect(count).toBe(0);
+      $rootScope.$digest();
+      expect(count).toBe(3);
+    }));
+
+    it('should run a $$postDigest call even if the child scope is isolated', inject(function($rootScope) {
+      var parent = $rootScope.$new(),
+          child = parent.$new(true),
+          signature = '';
+
+      parent.$$postDigest(function() {
+        signature += 'A';
+      });
+
+      child.$$postDigest(function() {
+        signature += 'B';
+      });
+
+      expect(signature).toBe('');
+      $rootScope.$digest();
+      expect(signature).toBe('AB');
+    }));
+  });
 
   describe('events', function() {