This keyword suggests that future versions of JavaScript may support the goto statement which will unconditionally go to a labelled portion of script source text. This also suggests that labels will need to be supported as well.

ECMA edition 3 already mandates that case and default labels are supported for the benefit of the switch() statement.

The ECMA standard notes that although it is reserved future use, an implementation is still compliant if it provides the appropriate functionality of these reserved keywords.

Cross-references:

ECMA 262 edition 2 - section - 7.4.3

ECMA 262 edition 3 - section - 7.5.3