diff --git a/DScript.Demo/testscript.js b/DScript.Demo/testscript.js
index af89758..510d67c 100644
--- a/DScript.Demo/testscript.js
+++ b/DScript.Demo/testscript.js
@@ -1,12 +1,12 @@
-var MyClass = {
-    doSomethingComplicated: function (x, y) {
-        this.doSomethingElse(x, y);
-    },
-
-    doSomethingElse: function (a,b) {
-
-        return Math.pow(--a, ++b) / 10.0;
-    }
+const testStr = "For more information, see Chapter 3.4.5.1";
+
+function MyClass() {
+    this.doSomethingComplicated = function (x, y) {
+        return this.doSomethingElse(x, y);
+    };
+    this.doSomethingElse = function (a, b) {
+        return Math.pow(a, b) / 10.0;
+    };
 };
 
 var inst = new MyClass();
@@ -17,7 +17,7 @@ console.log(x);
 var to = typeof x;
 
 var p = to == "number" ? "yes" : "no";
-var testString = "For more information, see Chapter 3.4.5.1";
+var testString = testStr;
 var myRegex = /see (chapter \d+(\.\d)*)/i;
 
 var matches = testString.match(myRegex);
@@ -38,11 +38,10 @@ catch (ex) {
 }
 
 try {
-
-    var x = 1;
+    testStr = "123";
 }
 catch (ex) {
-
+    console.log(ex);
 }
 finally {
 
diff --git a/DScript/ScriptEngine.Statement.cs b/DScript/ScriptEngine.Statement.cs
index b7c0192..4c7ceee 100644
--- a/DScript/ScriptEngine.Statement.cs
+++ b/DScript/ScriptEngine.Statement.cs
@@ -38,19 +38,21 @@ private void Statement(ref bool execute)
                 //allow for multiple semi colon such as ;;;
                 currentLexer.Match((ScriptLex.LexTypes)';');
             }
-            else if (currentLexer.TokenType == ScriptLex.LexTypes.RVar)
+            else if (currentLexer.TokenType == ScriptLex.LexTypes.RVar || currentLexer.TokenType == ScriptLex.LexTypes.RConst)
             {
                 //creating variables
                 //TODO: make this less shit
 
-                currentLexer.Match(ScriptLex.LexTypes.RVar);
+                var readOnly = currentLexer.TokenType == ScriptLex.LexTypes.RConst;
+
+                currentLexer.Match(currentLexer.TokenType);
 
                 while (currentLexer.TokenType != (ScriptLex.LexTypes)';')
                 {
                     ScriptVarLink a = null;
                     if (execute)
                     {
-                        a = scopes.Back().FindChildOrCreate(currentLexer.TokenString);
+                        a = scopes.Back().FindChildOrCreate(currentLexer.TokenString, ScriptVar.Flags.Undefined, readOnly);
                     }
 
                     currentLexer.Match(ScriptLex.LexTypes.Id);
diff --git a/DScript/ScriptEngine.cs b/DScript/ScriptEngine.cs
index 68ba97d..29de250 100644
--- a/DScript/ScriptEngine.cs
+++ b/DScript/ScriptEngine.cs
@@ -118,19 +118,20 @@ public void Execute(string code)
                     {
                         Statement(ref execute);
                     }
-                    catch (ScriptException ex)
+                    catch (Exception ex)
                     {
-                        var errorMessage = new StringBuilder(string.Format("ERROR on line {0} column {1} [{2}]", currentLexer.LineNumber, currentLexer.ColumnNumber, ex.Message));
+                        if (ex is ScriptException || ex is JITException)
+                        {
+                            var errorMessage = new StringBuilder(string.Format("ERROR on line {0} column {1} [{2}]", currentLexer.LineNumber, currentLexer.ColumnNumber, ex.Message));
+
+                            Console.Error.WriteLine(errorMessage.ToString());
 
-                        int i = 0;
-                        foreach (ScriptVar scriptVar in scopes)
+                            return;
+                        }
+                        else
                         {
-                            errorMessage.AppendLine();
-                            errorMessage.Append(i++ + ": " + scriptVar);
+                            throw;
                         }
-
-                        Console.Error.WriteLine(errorMessage.ToString());
-                        throw;
                     }
                 }
             }
diff --git a/DScript/ScriptLex.cs b/DScript/ScriptLex.cs
index e6b7242..5fa0b47 100644
--- a/DScript/ScriptLex.cs
+++ b/DScript/ScriptLex.cs
@@ -130,6 +130,7 @@ public enum LexTypes
             RCatch,
             RFinally,
             RThrow,
+            RConst,
             RListEnd
         }
 
@@ -257,6 +258,7 @@ public void GetNextToken()
                     case "catch": TokenType = LexTypes.RCatch; break;
                     case "finally": TokenType = LexTypes.RFinally; break;
                     case "throw": TokenType = LexTypes.RThrow; break;
+                    case "const": TokenType = LexTypes.RConst; break;
                 }
             }
             else if (CurrentChar.IsNumeric()) //Numbers
diff --git a/DScript/ScriptVar.cs b/DScript/ScriptVar.cs
index cb9d380..4e8fafc 100644
--- a/DScript/ScriptVar.cs
+++ b/DScript/ScriptVar.cs
@@ -440,12 +440,12 @@ public ScriptVarLink FindChild(string childName)
             return null;
         }
 
-        public ScriptVarLink FindChildOrCreate(string childName, Flags varFlags = Flags.Undefined)
+        public ScriptVarLink FindChildOrCreate(string childName, Flags varFlags = Flags.Undefined, bool readOnly = false)
         {
             var l = FindChild(childName);
             if (l != null) return l;
 
-            return AddChild(childName, new ScriptVar(null, varFlags));
+            return AddChild(childName, new ScriptVar(null, varFlags), readOnly);
         }
 
         public ScriptVarLink FindChildOrCreateByPath(string path)
@@ -458,7 +458,7 @@ public ScriptVarLink FindChildOrCreateByPath(string path)
             return FindChildOrCreate(parts[0], Flags.Object).Var.FindChildOrCreateByPath(parts[1]);
         }
 
-        public ScriptVarLink AddChild(string childName, ScriptVar child)
+        public ScriptVarLink AddChild(string childName, ScriptVar child, bool readOnly = false)
         {
             if (IsUndefined)
             {
@@ -467,7 +467,7 @@ public ScriptVarLink AddChild(string childName, ScriptVar child)
 
             var c = child ?? new ScriptVar();
 
-            var link = new ScriptVarLink(c, childName)
+            var link = new ScriptVarLink(c, childName, readOnly)
             {
                 Owned = true
             };
diff --git a/DScript/ScriptVarLink.cs b/DScript/ScriptVarLink.cs
index 057f2f5..ab1f847 100644
--- a/DScript/ScriptVarLink.cs
+++ b/DScript/ScriptVarLink.cs
@@ -54,14 +54,16 @@ protected virtual void Dispose(bool disposing)
         public ScriptVarLink Prev { get; internal set; }
         public ScriptVar Var { get; internal set; }
         public bool Owned { get; internal set; }
+        public bool IsConst { get; private set; }
 
-        public ScriptVarLink(ScriptVar var, string name)
+        public ScriptVarLink(ScriptVar var, string name, bool readOnly = false)
         {
             Name = name;
             Var = var.Ref();
             Next = null;
             Prev = null;
             Owned = false;
+            IsConst = readOnly;
         }
 
         public ScriptVarLink(ScriptVarLink toCopy)
@@ -75,6 +77,11 @@ public ScriptVarLink(ScriptVarLink toCopy)
 
         public void ReplaceWith(ScriptVar newVar)
         {
+            if(IsConst && Var?.IsUndefined == false)
+            {
+                throw new JITException(string.Format("{0} is const, cannot assign a new value", Name));
+            }
+
             var oldVar = Var;
             Var = newVar.Ref();
             oldVar.UnRef();
@@ -82,6 +89,7 @@ public void ReplaceWith(ScriptVar newVar)
 
         public void ReplaceWith(ScriptVarLink newVar)
         {
+
             ReplaceWith(newVar != null ? newVar.Var : new ScriptVar());
         }