The tag is present in Lintian version 2.108.13. That is the most recent version we know about.
The source file includes a line length that is well beyond the normally human made code line length.
This very long line length does not allow Lintian to do correctly some source file checks.
This line could also be the result of some text injected by a computer program, and thus could lead to FTBFS bugs.
Last but not least, long line in source code could be used to obfuscate the source code and to hide stuff like backdoors or security problems.
It could be due to jslint source comments or other build tool comments.
You may report this issue upstream.