diff --git a/weboob/tools/js.py b/weboob/tools/js.py
new file mode 100644
index 00000000..64ad8f78
--- /dev/null
+++ b/weboob/tools/js.py
@@ -0,0 +1,57 @@
+# -*- coding: utf-8 -*-
+
+# Copyright(C) 2015      Romain Bignon
+#
+# This file is part of weboob.
+#
+# weboob is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# weboob is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with weboob. If not, see <http://www.gnu.org/licenses/>.
+
+
+__all__ = ['Javascript']
+
+
+class Javascript(object):
+    HEADER = """
+  function btoa(str) {
+    var buffer
+      ;
+
+    if (str instanceof Buffer) {
+      buffer = str;
+    } else {
+      buffer = new Buffer(str.toString(), 'binary');
+    }
+
+    return buffer.toString('base64');
+  }
+
+  function atob(str) {
+    return new Buffer(str, 'base64').toString('binary');
+  }
+
+  var document = {};
+    """
+
+    def __init__(self, script):
+        try:
+            import execjs
+        except ImportError:
+            raise ImportError('Please install PyExecJS')
+
+        self.runner = execjs.get()
+
+        self.ctx = self.runner.compile(self.HEADER + script)
+
+    def call(self, *args, **kwargs):
+        return self.ctx.call(*args, **kwargs)