perf($parse): optimize filter implementation

IgorMinar · IgorMinar · commit ece6ef479c74 · 2014-08-18T21:20:12.000-07:00
- generate less garbage
- optimize argument collection
- use call instead of apply for no arg case (2x boost)
diff --git a/src/ng/parse.js b/src/ng/parse.js
@@ -550,19 +550,31 @@ Parser.prototype = {
   filter: function() {
     var token = this.expect();
     var fn = this.$filter(token.text);
-    var argsFn = [];
-    while(this.expect(':')) {
-      argsFn.push(this.expression());
-    }
-    return valueFn(fnInvoke);
+    var argsFn;
+    var args;
 
-    function fnInvoke(self, locals, input) {
-      var args = [input];
-      for (var i = 0; i < argsFn.length; i++) {
-        args.push(argsFn[i](self, locals));
+    if (this.peek(':')) {
+      argsFn = [];
+      args = []; // we can safely reuse the array
+      while (this.expect(':')) {
+        argsFn.push(this.expression());
       }
-      return fn.apply(self, args);
     }
+
+    return valueFn(function $parseFilter(self, locals, input) {
+      if (args) {
+        args[0] = input;
+
+        var i = argsFn.length;
+        while (i--) {
+          args[i + 1] = argsFn[i](self, locals);
+        }
+
+        return fn.apply(self, args);
+      }
+
+      return fn.call(self, input);
+    });
   },
 
   expression: function() {
