diff --git a/astar.js b/astar.js
index 8a25115..bb57b1d 100644
--- a/astar.js
+++ b/astar.js
@@ -283,34 +283,37 @@ function BinaryHeap(scoreFunction) {
 
 BinaryHeap.prototype = {
   push: function(element) {
+    var content = this.content;
     // Add the new element to the end of the array.
-    this.content.push(element);
+    content.push(element);
 
     // Allow it to sink down.
-    this.sinkDown(this.content.length - 1);
+    this.sinkDown(content.length - 1);
   },
   pop: function() {
+    var content = this.content;
     // Store the first element so we can return it later.
-    var result = this.content[0];
+    var result = content[0];
     // Get the element at the end of the array.
-    var end = this.content.pop();
+    var end = content.pop();
     // If there are any elements left, put the end element at the
     // start, and let it bubble up.
-    if (this.content.length > 0) {
-      this.content[0] = end;
+    if (content.length !== 0 ) {
+      content[0] = end;
       this.bubbleUp(0);
     }
     return result;
   },
   remove: function(node) {
-    var i = this.content.indexOf(node);
+    var content = this.content;
+    var i = content.indexOf(node);
 
     // When it is found, the process seen in 'pop' is repeated
     // to fill up the hole.
-    var end = this.content.pop();
+    var end = content.pop();
 
-    if (i !== this.content.length - 1) {
-      this.content[i] = end;
+    if (i !== content.length - 1) {
+      content[i] = end;
 
       if (this.scoreFunction(end) < this.scoreFunction(node)) {
         this.sinkDown(i);
@@ -326,19 +329,22 @@ BinaryHeap.prototype = {
     this.sinkDown(this.content.indexOf(node));
   },
   sinkDown: function(n) {
+    var content = this.content;
+    var scoreFunction = this.scoreFunction;
     // Fetch the element that has to be sunk.
-    var element = this.content[n];
-
+    var element = content[n];
+    //
+    var elemScore = scoreFunction(element);
+    var parentN = 0, parent = 0;
     // When at 0, an element can not sink any further.
     while (n > 0) {
-
       // Compute the parent element's index, and fetch it.
-      var parentN = ((n + 1) >> 1) - 1;
-      var parent = this.content[parentN];
+      parentN = ((n + 1) >> 1) - 1;
+      parent = content[parentN];
       // Swap the elements if the parent is greater.
-      if (this.scoreFunction(element) < this.scoreFunction(parent)) {
-        this.content[parentN] = element;
-        this.content[n] = parent;
+      if (elemScore < scoreFunction(parent)) {
+        content[parentN] = element;
+        content[n] = parent;
         // Update 'n' to continue at the new position.
         n = parentN;
       }
@@ -349,23 +355,29 @@ BinaryHeap.prototype = {
     }
   },
   bubbleUp: function(n) {
+    var content = this.content;
+    var scoreFunction = this.scoreFunction;
     // Look up the target element and its score.
-    var length = this.content.length;
-    var element = this.content[n];
-    var elemScore = this.scoreFunction(element);
+    var length = content.length;
+    var element = content[n];
+    var elemScore = scoreFunction(element);
+    // early declarations with type hints
+    var child2N = 0, child1N = 0;
+    var child1Score=0;
+    var swap = -1 ;    // no type change !! -1 stands for no swap. X2 speed increase !!!
+    var child1=null, child2 = null;
 
     while (true) {
       // Compute the indices of the child elements.
-      var child2N = (n + 1) << 1;
-      var child1N = child2N - 1;
+      child2N = (n + 1) << 1;
+      child1N = child2N - 1;
       // This is used to store the new position of the element, if any.
-      var swap = null;
-      var child1Score;
+      swap = -1 ;
       // If the first child exists (is inside the array)...
       if (child1N < length) {
         // Look it up and compute its score.
-        var child1 = this.content[child1N];
-        child1Score = this.scoreFunction(child1);
+        child1 = content[child1N];
+        child1Score = scoreFunction(child1);
 
         // If the score is less than our element's, we need to swap.
         if (child1Score < elemScore) {
@@ -375,17 +387,16 @@ BinaryHeap.prototype = {
 
       // Do the same checks for the other child.
       if (child2N < length) {
-        var child2 = this.content[child2N];
-        var child2Score = this.scoreFunction(child2);
-        if (child2Score < (swap === null ? elemScore : child1Score)) {
+        child2 = content[child2N];
+        if ( scoreFunction(child2) < (swap < 0 ? elemScore : child1Score)) {
           swap = child2N;
         }
       }
 
       // If the element needs to be moved, swap it, and continue.
-      if (swap !== null) {
-        this.content[n] = this.content[swap];
-        this.content[swap] = element;
+      if (swap >= 0 ) {
+        content[n] = content[swap];
+        content[swap] = element;
         n = swap;
       }
       // Otherwise, we are done.
@@ -401,4 +412,4 @@ return {
   Graph: Graph
 };
 
-});
\ No newline at end of file
+});