diff --git a/lib/ace/ext/beautify.js b/lib/ace/ext/beautify.js
index 9fa23399701..41fb1357c7c 100644
--- a/lib/ace/ext/beautify.js
+++ b/lib/ace/ext/beautify.js
@@ -103,7 +103,7 @@ exports.beautify = function(session) {
         breakBefore = false;
     };
 
-    while (token !== null) {
+    var prettify = function (){
         curRow = iterator.getCurrentTokenRow();
         rowTokens = iterator.$rowTokens;
         nextToken = iterator.stepForward();
@@ -409,9 +409,29 @@ exports.beautify = function(session) {
 
         token = nextToken;
     }
-
-    code = code.trim();
-    session.doc.setValue(code);
+    var id;
+    if(window.requestAnimationFrame){
+        id = requestAnimationFrame(function loop (){
+            if(token !== null) {
+                try{
+                    prettify();
+                    id = requestAnimationFrame(loop);
+                }catch(e){
+                    console.warn('requestAnimationFrame has been interupted',id);
+                    cancelAnimationFrame(id);
+                }
+            }else{
+               code = code.trim();
+               session.doc.setValue(code);   
+           }
+       })
+    }else{
+        while(token !== null) {
+            step();
+        }
+        code = code.trim();
+        session.doc.setValue(code);   
+    }
 };
 
 exports.commands = [{