This test checks that toString() round-trip on a function that has a typeof operator applied to a group expression will not remove the grouping. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS unevalf(eval(unevalf(typeof_should_preserve_parens))) is unevalf(typeof_should_preserve_parens) PASS /.*\(+x\)*, y\)/.test(unevalf(typeof_should_preserve_parens)) is true PASS typeof_should_preserve_parens('a', 1); is 'number' PASS eval(unevalf(typeof_should_preserve_parens))('a', 1); is 'number' PASS unevalf(eval(unevalf(typeof_should_preserve_parens1))) is unevalf(typeof_should_preserve_parens1) PASS /.*\(+x\)*, y\)/.test(unevalf(typeof_should_preserve_parens1)) is true PASS typeof_should_preserve_parens1('a', 1); is 'number' PASS eval(unevalf(typeof_should_preserve_parens1))('a', 1); is 'number' PASS unevalf(eval(unevalf(typeof_should_preserve_parens2))) is unevalf(typeof_should_preserve_parens2) PASS /.*\(+x\)*, y\)/.test(unevalf(typeof_should_preserve_parens2)) is true PASS typeof_should_preserve_parens2('a', 1); is 'number' PASS eval(unevalf(typeof_should_preserve_parens2))('a', 1); is 'number' PASS unevalf(eval(unevalf(typeof_should_preserve_parens_multi))) is unevalf(typeof_should_preserve_parens_multi) PASS /.*\(+x\)*, y\)/.test(unevalf(typeof_should_preserve_parens_multi)) is true PASS typeof_should_preserve_parens_multi('a', 1); is 'number' PASS eval(unevalf(typeof_should_preserve_parens_multi))('a', 1); is 'number' PASS successfullyParsed is true TEST COMPLETE