merkle tree update - getIndexByElement

lib/MerkleTree.js

@@ -179,6 +179,16 @@ class MerkleTree {
       current_index = Math.floor(current_index / 2)
     }
   }
+
+  getIndexByElement(element) {
+    for(let i = this.totalElements - 1; i >= 0; i--) {
+      const elementFromTree = this.storage.get(MerkleTree.index_to_key(this.prefix, 0, i))
+      if (elementFromTree === element) {
+        return i
+      }
+    }
+    return false
+  }
 }
 
 module.exports = MerkleTree