Iterator performance enhancements - turn hasNext and peek into element access, and...

[dygraphs.git] / dygraph-utils.js

diff --git a/dygraph-utils.js b/dygraph-utils.js
index 8cfd861..7aeca8d 100644 (file)
--- a/dygraph-utils.js
+++ b/dygraph-utils.js
@@ -684,46 +684,37 @@ Dygraph.isAndroid = function() {
 Dygraph.Iterator = function(array, start, length, predicate) {
   start = start || 0;
   length = length || array.length;
+  this.hasNext = true; // Use to identify if there's another element.
+  this.peek = null; // Use for look-ahead
   this.array_ = array;
   this.predicate_ = predicate;
   this.end_ = Math.min(array.length, start + length);
-  this.nextIdx_ = start - 1; // use -1 so initial call to advance works.
-  this.hasNext_ = true;
-  this.peek_ = null;
-  this.advance_();
-}
-
-Dygraph.Iterator.prototype.hasNext = function() {
-  return this.hasNext_;
+  this.nextIdx_ = start - 1; // use -1 so initial advance works.
+  this.next(); // ignoring result.
 }
 
 Dygraph.Iterator.prototype.next = function() {
-  if (this.hasNext_) {
-    var obj = this.peek_;
-    this.advance_();
-    return obj;
+  if (!this.hasNext) {
+    return null;
   }
-  return null;
-}
+  var obj = this.peek;
 
-Dygraph.Iterator.prototype.peek = function() {
-  return this.peek_;
-}
-
-Dygraph.Iterator.prototype.advance_ = function() {
-  var nextIdx = this.nextIdx_;
-  nextIdx++;
-  while(nextIdx < this.end_) {
+  var nextIdx = this.nextIdx_ + 1;
+  var found = false;
+  while (nextIdx < this.end_) {
     if (!this.predicate_ || this.predicate_(this.array_, nextIdx)) {
-      this.peek_ = this.array_[nextIdx];
-      this.nextIdx_ = nextIdx;
-      return;
+      this.peek = this.array_[nextIdx];
+      found = true;
+      break;
     }
     nextIdx++;
   }
   this.nextIdx_ = nextIdx;
-  this.hasNext_ = false;
-  this.peek_ = null;
+  if (!found) {
+    this.hasNext = false;
+    this.peek = null;
+  }
+  return obj;
 }
 
 /**