Routes with Non Participating Capture Groups exec() differently in old IE browsers

[ericf]

We recently fixed issue #964 to support Non Participating Capture Groups (NPCG) in regex Router paths. But the tests for this change were not run in IE < 9, and when they are subtle differences are surfaced in how old IEs vs. modern browsers deal with NPCG when calling the regex's exec() method. The following example illustrates the issue:

var route = /\/foo\/(bar)?/;

// In modern browsers:
console.log(route.exec('/foo/')); // => ["/foo/", undefined]

// In IE < 9:
console.log(route.exec('/foo/')); // => ["/foo/", ""]

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In the context of route dispatching in Router, the result of exec()-ing the regex route path is assigned to req.params. Since request parameters are dealing with strings, I think a fine compromise is to always make sure they are an array of strings and coerce undefined to empty string, both are falsy values.

[evocateur]

+1