diff --git a/boot/boot.js b/boot/boot.js
index acdfa0327..68eb80799 100644
--- a/boot/boot.js
+++ b/boot/boot.js
@@ -84,6 +84,15 @@ $tw.utils.each = function(object,callback) {
 	}
 };
 
+/*
+Pushes a value to an array only when not yet contained.
+*/
+$tw.utils.pushOnce = function(array,value) {
+	if(0 > array.indexOf(value)){
+		array.push(value);
+	}
+}
+
 /*
 Helper for making DOM elements
 tag: tag name