Set a really long expiration on your static assets, then expose the returned function to res.locals. The 'v' query parameter should be an option, but I'm lazy.

staticUrl.js

var crc = require("crc");
var fs = require("fs");
var path = require("path");

var staticUrl = function(static_path, options) {
  static_path = path.resolve(static_path);
  options = options || {};
  var cache = {};
  var prefix = options.prefix || '';
  var check_mtime = !options.cache;

  return function(asset) {
    var filename = static_path + "/" + asset;
    var info = cache[filename];
    if (!check_mtime && info) {
      return prefix + asset + '?v=' + info.tag;
    }

    if (!fs.existsSync(filename)) {
      info = { mtime: 0, tag: '' };
    } else {
      var stats = fs.statSync(filename);
      var mtime = stats.mtime.getTime();
      if (!info || mtime > info.mtime) {
        var data = fs.readFileSync(filename);
        var hash = crc.buffer.crc32(data) + 0x80000000;
        var tag = stats.size.toString(36) + '-' + hash.toString(36);
        info = { mtime: mtime, tag: tag };
      }
    }

    cache[filename] = info;
    return prefix + asset + '?v=' + info.tag;
  }
};

module.exports = staticUrl;