diff --git a/orderBook.js b/orderBook.js
new file mode 100644
index 0000000..34cf7f8
--- /dev/null
+++ b/orderBook.js
@@ -0,0 +1,41 @@
+function reconcileOrder(existingBook, incomingOrder) {
+    let updates = []
+    let newOrders = []
+  
+    if (!existingBook.length) {
+        updates.push(incomingOrder)
+    
+        return updates
+      }
+    
+      for (let i = 0; i < existingBook.length; i++) {
+        if (existingBook[i].type !== incomingOrder.type &&
+            existingBook[i].price === incomingOrder.price &&
+            existingBook[i].quantity === incomingOrder.quantity) {
+            incomingOrder.price = -1
+
+        } else if (existingBook[i].type !== incomingOrder.type &&
+            existingBook[i].price === incomingOrder.price &&
+            existingBook[i].quantity !== incomingOrder.quantity) {
+                
+                if (existingBook[i].quantity > incomingOrder.quantity) {
+                    existingBook[i].quantity = existingBook[i].quantity - incomingOrder.quantity
+                    incomingOrder.quantity = 0
+                    newOrders.push(existingBook[i])
+
+                } else {
+                    incomingOrder.quantity = incomingOrder.quantity - existingBook[i].quantity
+                  }
+                } else {
+                  updates.push(existingBook[i])
+                }
+              }
+              if (incomingOrder.price !== -1 && incomingOrder.quantity !== 0) {
+                updates.push(incomingOrder)
+              }
+            
+              return updates.concat(newOrders)
+            }
+            
+            module.exports = {reconcileOrder}
+        
\ No newline at end of file