Discuss
  • {this} object literal

{this} object literal

# Michał Wadas (8 years ago)

Is there any specific reason why {this} literal is forbidden? Babel had a bug allowing this and it was pretty convenient to enter console.log({this, arguments, externalVar}) for quick printing scope.

Michał Wadas

# Sam Gluck (8 years ago)

Regardless of whether this is permitted as the property name of an object, why not use console.log(this, arguments, externalVar)? (Out of interest)

On 21 Apr 2017 6:01 p.m., "Michał Wadas" <michalwadas at gmail.com> wrote:

Hi.

Is there any specific reason why {this} literal is forbidden? Babel had a bug allowing this and it was pretty convenient to enter console.log({this, arguments, externalVar}) for quick printing scope.

Michał Wadas

# Gary Guo (8 years ago)

Because the shorthand only requires an Identifer, and an IdentiferName is not sufficient. If the rule allows arbitrary IdentiferName, then we will also allow {if}, which makes no sense it all. So if we really want to allow this, it would be a special rule in addition to the current rule. In this sense, we are not forbidden the use of {this}, but instead we don't have the rule to allow that.

# Claude Pache (8 years ago)

More generally, all keywords are excluded, that makes sense in general as, e.g., { if } could not be equivalent to { if: if }, or { yield } inside a generator function should not be equivalent to { yield: yield }.

But yes, one could have special-cases for literals such as this, true, false and null. It is an accident of history that { NaN } and { undefined } work as expected, but not { null }.

# Gary Guo (8 years ago)

Because the shorthand requires an Identifer, and an IdentiferName is not sufficient. If the rule allows arbitrary IdentiferName, then we will also allow {if}, which makes no sense it all. So if we really want to allow this, it would be a special rule in addition to the current rule. In this sense, we are not forbidden the use of {this}, but instead we don't have the rule to allow that.