In particular, this changes the behavior of NodeJS in the following ways:
- Any attempt to get or modify the global object will result in an error.
- null values of this will no longer be evaluated to the global object and primitive values of this will not be converted to wrapper objects.
- Writing or deleting properties which have there writeable or configurable attributes set to false will now throw an error instead of failing silently.
- Adding a property to an object whose extensible attribute is false will also throw an error now.
- A functions arguments are not writeable so attempting to change them will now throw an error arguments = [...].
- with(){} statements are gone.
- Use of eval is effectively banned.
- eval and arguments are not allowed as variable or function identifiers in any scope.
- The identifiers implements, interface, let, package, private, protected, public, static and yield are all now reserved for future use (roll on ES6).