delete or override const variables in javascript Harmony / ECMAScript 6

Question

Reading and tinkering with the new features offered by ECMAScript 6.

The new 'const' statement for writing constant variables is a nifty feature, which adds features to an already interesting update.

The variable is created as read-only, and once it is stated it can't be overridden.

EDIT: A consequent problem arise, for example, when testing code on the console. Running a script containing a const definition twice, would lead to an error, breaking the execution.

What if I want to release that keyword? Is there any way to unset or delete the variable?

I've read in this post that this is actually a problem which affects the var statement as well, because the environments where the variables are created are different on many level of abstraction.

How ECMAScript 6 intend to address this issue?

Answer 1

It is not possible to redefine variables declared using const.

However, const is block-scoped. To address the issue you describe, when testing some code in the console all you would have to do is wrap your script in { and }:

{ const x = 1; }
{ const x = 2; }

Note that many browsers that already support the const keyword do not yet support block-scoped constants so the example above will fail in Chrome and Firefox (See Kangax's compatibility table for more).