FindClosest function added to treebase.js

lib/treebase.js

@@ -24,6 +24,40 @@ TreeBase.prototype.find = function(data) {
     return null;
 };
 
+// returns node data closest to supplied value.
+TreeBase.prototype.findClosest = function(data){
+  var res = this._root;
+  var lastSmallerNode = null;
+  var lastSmallerC = null;
+  var lastLargerNode = null;
+  var lastLargerC = null;
+
+  while(res !== null){
+      var c = this._comparator(data, res.data);
+      if(c === 0) {
+        return res.data;
+      }
+      else {
+        if(c < 0) {
+          lastLargerC = c;
+          lastLargerNode = res;
+        }
+        else if(c > 0){
+          lastSmallerC = c;
+          lastSmallerNode = res;
+        }
+        res = res.get_child(c > 0);
+      }
+  }
+
+    // will reach here only if it reaches a null node
+  if(lastSmallerC === null && lastLargerC === null) return null; // nothing in rbtree
+  var absSmall = Math.abs(lastSmallerC);
+  var absLarge = Math.abs(lastLargerC);
+  if (absSmall == absLarge) return lastSmallerNode.data;
+  return absSmall < absLarge ? lastSmallerNode.data : lastLargerNode.data;
+};
+
 // returns iterator to node if found, null otherwise
 TreeBase.prototype.findIter = function(data) {
     var res = this._root;