Implements group in status code metrics

src/normalizeStatusCode.js

@@ -0,0 +1,22 @@
+'use strict';
+
+module.exports = function(req, opts) {
+  opts = opts || {};
+
+  if (opts.formatStatusCode !== undefined && !opts.formatStatusCode) {
+    return req.status_code;
+  }
+  if (typeof opts.formatStatusCode === 'function') {
+    return opts.formatStatusCode(req, opts);
+  }
+
+  // Group Status code in 1xx, 2xx, 3xx, 4xx, 5xx or other
+  const status_code = ({
+    '1': '1xx',
+    '2': '2xx',
+    '3': '3xx',
+    '4': '4xx',
+    '5': '5xx',
+  })[(req.status_code || '').substr(0,1)] || 'other';
+  return status_code;
+};