From a08087c5e8429cb4fdff4f34cfd31c960140c8bf Mon Sep 17 00:00:00 2001
From: Hornwitser <github@hornwitser.no>
Date: Fri, 20 Nov 2020 01:32:32 +0100
Subject: [PATCH] Optimize escapeLabelValue for the common case

Avoid an expensive string copy for the common case of there being no
characters to escape in the label value.
---
 packages/lib/prometheus.js | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/packages/lib/prometheus.js b/packages/lib/prometheus.js
index cf25b6a3..9a9bda69 100644
--- a/packages/lib/prometheus.js
+++ b/packages/lib/prometheus.js
@@ -206,6 +206,7 @@ class Collector {
 	async* collect() { }
 }
 
+const labelEscapesChars = /[\\\n\"]/;
 /**
  * Escapes a label value in accordance with the text exposition format
  *
@@ -214,6 +215,9 @@ class Collector {
  * @private
  */
 function escapeLabelValue(value) {
+	if (!labelEscapesChars.test(value)) {
+		return value;
+	}
 	return value
 		.replace(/\\/g, "\\\\")
 		.replace(/\n/g, "\\n")