Javascript代码解析及常量

Question

Given there is no cross browser const in Javascript and most of the work-arounds are more complex than I care for, I am just going to go with the naming convention of THIS_IS_A_CONSTANT. All well and good, but what occurred to me is that if there was way to get my IDE (VS.NET 2010 with Resharper 6) to give me a warning on any Javascript code that makes an assignment to a variable with that naming convention except in the variable declaration this would handle most of the potential issues around the lack of real constants in Javascript (at least for my needs).

So does anyone know of a good way to generate such warnings? In-IDE would be the best thing but other solutions are fine as well. I have looked for something like FX-Cop for Javascript; jslint doesn't seem to allow the creation of new rules but maybe I didn't look deep enough. I may also suggest this as a feature in Resharper (assuming I am not missing a way to make it do so already).

Thanks, Matthew

Answer 1

So you want to find any assigment of the form:

id = exp ;

where id doesn't contain the substring CONSTANT and exp is a numeric constant?

Our Source Code Search Engine (SCSE) can do this pretty directly. The SCSE reads source code for a large set of files for many languages (including JavaScript), breaks it into tokens ignoring whitespace , and indexes it all to enable fast search for token sequences. Any hits are displayed in a hit window and can be clicked to see the actual file text in context.

Your particular query would be stated:

  (I - I=*CONSTANT*) '=' N ( ';' | O | K | I)

This hunts for any assignment in which the target identifier doesn't contain the string constant (see wildcard stars around the match string), assigned a constant * N *umber is not followed by a ';' or an * O *perator, * K *word or * I *dentifier (all this extra stuff is because JavaScript might not have a semicolon to terminate the statement). It probably picks up some cases it should not but these are easily inspected.