Bugs in negated `in` expressions

[Pablo Gorostiaga]

in and instanceof expressions in JS

a in obj;
a instanceof C;

can be negated by grouping them and applying the ! operator, i.e.

!(a in obj);
!(a instanceof C);

Applying the ! operator incorrectly (on the LHS operand) leads to bugs:

!a in obj; // will evaluate to false, unless obj has a "true" or "false" key
!a instanceof C; // will evaluate to false, unless C overrides instanceof with a @@hasInstance method

For more information, please see these MDN docs and the no-unsafe-negation recommended Eslint rule.

I have found a potentially problematic instance of the above bugs in your codebase:

microservices-platform/zlt-web/layui-web/src/main/resources/static/assets/libs/q.js

Line 38 in da821d6

 if (!'onhashchange' in W) {