diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/sample/nashorn/findvardelete.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/sample/nashorn/findvardelete.js	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   - Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *
+ *   - Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *
+ *   - Neither the name of Oracle nor the names of its
+ *     contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+// delete of scope vars is reported as error in strict mode.
+// This script finds scripts that such deletes. Scripts in
+// the specified directory are scanned. If no directory is 
+// specified, the current directory is scanned.
+
+if (arguments.length == 0) {
+    arguments[0] = ".";
+}
+
+var File = Java.type("java.io.File");
+var file = new File(arguments[0]);
+if (!file.exists()) {
+    print(arguments[0] + " is neither a directory nor a file");
+    exit(1);
+}
+
+var Files = Java.type("java.nio.file.Files");
+var IdentifierTree = Java.type("jdk.nashorn.api.tree.IdentifierTree");
+var Parser = Java.type("jdk.nashorn.api.tree.Parser");
+var SimpleTreeVisitor = Java.type("jdk.nashorn.api.tree.SimpleTreeVisitorES5_1");
+var Tree = Java.type("jdk.nashorn.api.tree.Tree");
+
+var parser = Parser.create("-scripting", "--const-as-var");
+
+function checkFile(file) {
+    // print("checking " + file);
+    var ast = parser.parse(file, print);
+    if (!ast) {
+        return;
+    }
+
+    // locate __proto__ usage and warn
+    ast.accept(visitor = new (Java.extend(SimpleTreeVisitor)) {
+        lineMap: null,
+
+        printWarning: function(node, varName) {
+            var pos = node.startPosition;
+            var line = this.lineMap.getLineNumber(pos);
+            var column = this.lineMap.getColumnNumber(pos);
+            print("WARNING: delete " + varName + " in " + file + " @ " + line + ":" + column);
+        },
+
+        visitCompilationUnit: function(node, extra) {
+            this.lineMap = node.lineMap;
+            Java.super(visitor).visitCompilationUnit(node, extra);
+        },
+
+        visitUnary: function(node, extra) {
+            if (node.kind == Tree.Kind.DELETE &&
+                node.expression instanceof IdentifierTree) {
+                this.printWarning(node, node.expression.name);
+            } 
+            Java.super(visitor).visitUnary(node, extra);
+        },
+
+    }, null);
+}
+
+if (file.isDirectory()) {
+    Files.walk(file.toPath())
+        .filter(function(p) Files.isRegularFile(p))
+        .filter(function(p) p.toFile().name.endsWith('.js'))
+        .forEach(checkFile);
+} else {
+    checkFile(file);
+}