perf: swap order of escape regexes to avoid lookahead (#546)

* swap regex order to avoid lookahead

* changelog

* changelog formatting apparently

CHANGELOG.md

@@ -13,9 +13,6 @@ project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Changed
 
-- Refactor `escapeString` helper in `lib/registry.js` to improve performance and
-  avoid an unnecessarily complex regex.
-
 ### Added
 
 - Support for OpenMetrics and Exemplars
@@ -27,6 +24,8 @@ project adheres to [Semantic Versioning](http://semver.org/).
 - Refactor `getMetricAsPrometheusString` method in the `Registry` class to use `Array.prototype.join`
   instead of loop of string concatenations.
 - Also use `Array.prototype.map`, and object spread instead of an explicit `for` loop
+- Refactor `escapeString` helper in `lib/registry.js` to improve performance and
+  avoid an unnecessarily complex regex.
 - changed: updated the sample output in `example/default-metrics.js`
 - `summary` metrics now has a `pruneAgedBuckets` config parameter
   to remove entries without any new values in the last `maxAgeSeconds`.

lib/registry.js

@@ -214,7 +214,7 @@ function escapeLabelValue(str) {
 	return escapeString(str).replace(/"/g, '\\"');
 }
 function escapeString(str) {
-	return str.replace(/\n/g, '\\n').replace(/\\(?!n)/g, '\\\\');
+	return str.replace(/\\/g, '\\\\').replace(/\n/g, '\\n');
 }
 function standardizeCounterName(name) {
 	return name.replace(/_total$/, '');