Using the following snippet in the ESQuery demo:

var f = "foo/bar";

None of these queries is parsed correctly and all fail with an error:

[value=/foo\/bar/]

Invalid regular expression: /foo/: \ at end of pattern

[value=/foo\\/bar/]

Expected " " or "]" but "b" found.

[value=/foo\\\\/bar/]

Expected " " or "]" but "b" found.

I'm using tsquery to write an import-location-specific TSLint rule for RxJS and the RegExp issue appears to be an upstream problem with this package.