[backend] fix: 修复异常处理和类型转换问题

frontend/node_modules/js-tokens/README.md

@@ -188,4 +188,53 @@ Secondly, not every character is a valid regex flag.
 var number = bar / 2/e
 ```
 
-The above example is also correctly identifie
+The above example is also correctly identified as division, because `e` is not a
+valid regex flag. I initially wanted to future-proof by allowing `[a-zA-Z]*`
+(any letter) as flags, but it is not worth it since it increases the amount of
+ambigous cases. So only the standard `g`, `m`, `i`, `y` and `u` flags are
+allowed. This means that the above example will be identified as division as
+long as you don’t rename the `e` variable to some permutation of `gmiyus` 1 to 6
+characters long.
+
+Lastly, we can look _forward_ for information.
+
+- If the token following what looks like a regex literal is not valid after a
+  regex literal, but is valid in a division expression, then the regex literal
+  is treated as division instead. For example, a flagless regex cannot be
+  followed by a string, number or name, but all of those three can be the
+  denominator of a division.
+- Generally, if what looks like a regex literal is followed by an operator, the
+  regex literal is treated as division instead. This is because regexes are
+  seldomly used with operators (such as `+`, `*`, `&&` and `==`), but division
+  could likely be part of such an expression.
+
+Please consult the regex source and the test cases for precise information on
+when regex or division is matched (should you need to know). In short, you
+could sum it up as:
+
+If the end of a statement looks like a regex literal (even if it isn’t), it
+will be treated as one. Otherwise it should work as expected (if you write sane
+code).
+
+### ES2018 ###
+
+ES2018 added some nice regex improvements to the language.
+
+- [Unicode property escapes] should allow telling names and invalid non-ASCII
+  characters apart without blowing up the regex size.
+- [Lookbehind assertions] should allow matching telling division and regex
+  literals apart in more cases.
+- [Named capture groups] might simplify some things.
+
+These things would be nice to do, but are not critical. They probably have to
+wait until the oldest maintained Node.js LTS release supports those features.
+
+[Unicode property escapes]: http://2ality.com/2017/07/regexp-unicode-property-escapes.html
+[Lookbehind assertions]: http://2ality.com/2017/05/regexp-lookbehind-assertions.html
+[Named capture groups]: http://2ality.com/2017/05/regexp-named-capture-groups.html
+
+
+License
+=======
+
+[MIT](LICENSE).