diff --git a/main.js b/main.js
index 1092e0d44c..372e5265d1 100644
--- a/main.js
+++ b/main.js
@@ -87,4 +87,22 @@ function microtime() {
     var now = new Date().getTime() / 1000;
 
     return now;
+}
+
+// accepting single level array with "value" as key
+function array_difference(firstArray, secondArray) {
+    var cloneArray = [];
+    
+    // create hardcopy
+    for (var i = 0; i < firstArray.length; i++) {
+        cloneArray.push(firstArray[i]);
+    }
+    
+    for (var i = 0; i < secondArray.length; i++) {
+        if (cloneArray.indexOf(secondArray[i]) != -1) {
+            cloneArray.splice(cloneArray.indexOf(secondArray[i]), 1);
+        }
+    }
+    
+    return cloneArray;
 }
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