From 61bd61012bc2725401060da0ec123521c1572180 Mon Sep 17 00:00:00 2001
From: MFA-G <fadhlanzap@gmail.com>
Date: Sun, 20 Sep 2026 20:18:15 +0700
Subject: [PATCH] fix: match the `format` argument like an input unit
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`parse('2MIN')` resolves fine because input units are lower-cased and
retried without a trailing `s`, but the `format` argument was looked up
verbatim on `parse.unit`. So `parse('2h', 'MIN')`, `parse('2h', 'mins')`
and `parse('2h', 'hrs')` all silently fell back to ms and returned
7200000 instead of 120 / 120 / 2 — a 60000x error with no signal.

`parse('2h', 'M')` was the worst case: `M` is a valid unit name in any
casing on the input side, so the caller gets a plausible-looking number
in the wrong unit.

Extract the input-side normalization into `lookupUnit` and use it for
both sides. An unrecognized format still falls back to ms.
---
 Readme.md |  1 +
 index.js  | 17 ++++++++++++++---
 test.js   | 17 +++++++++++++++++
 3 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/Readme.md b/Readme.md
index e8dc204..a3fc042 100644
--- a/Readme.md
+++ b/Readme.md
@@ -43,6 +43,7 @@ parse('2e3s')               // => 2000 * s
 
 // custom output format
 parse('1hr 20mins', 'm')    // => 80
+parse('1hr 20mins', 'MINS') // => 80, same matching rules as input units
 
 // add units
 parse.unit['μs'] = parse.unit.microsecond
diff --git a/index.js b/index.js
index 90380a5..23270ca 100644
--- a/index.js
+++ b/index.js
@@ -7,6 +7,18 @@ parse.unit = en
 // group/placeholder cleanup regex — rebuilt only when the locale strings change
 let groupRE, placeholder = null, group
 
+/**
+ * look up a unit name, ignoring case and a trailing plural `s`
+ *
+ * @param {object} unit
+ * @param {string} name
+ * @return {number|undefined}
+ */
+const lookupUnit = (unit, name) => {
+  name = String(name).toLowerCase()
+  return unit[name] ?? (name.endsWith('s') ? unit[name.slice(0, -1)] : undefined)
+}
+
 /**
  * convert `str` to ms
  *
@@ -35,12 +47,11 @@ export default function parse(str = '', format = 'ms') {
       }
       else units = format
     }
-    else units = units.toLowerCase()
 
-    prevUnits = units = unit[units] || (units.endsWith('s') ? unit[units.slice(0, -1)] : undefined)
+    prevUnits = units = lookupUnit(unit, units)
 
     if (typeof units == 'number') result = (result || 0) + m[1] * units
   }
 
-  return result && ((result / (unit[format] || 1)) * (str.trimStart()[0] === '-' ? -1 : 1))
+  return result && ((result / (lookupUnit(unit, format) || 1)) * (str.trimStart()[0] === '-' ? -1 : 1))
 }
diff --git a/test.js b/test.js
index f292ee3..5a7cfa7 100644
--- a/test.js
+++ b/test.js
@@ -158,6 +158,23 @@ t('format', t => {
 	t.end()
 })
 
+t('format is matched like an input unit', t => {
+	// upper-case, exactly as accepted on the input side (`parse('2MIN')`)
+	t.equal(parse('2h', 'M'), 120)
+	t.equal(parse('2h', 'MIN'), 120)
+	t.equal(parse('2h', 'Hours'), 2)
+
+	// plural, matching `unit.endsWith('s')` handling on the input side
+	t.equal(parse('2h', 'mins'), 120)
+	t.equal(parse('2h', 'hrs'), 2)
+	t.equal(parse('2h', 'seconds'), 7200)
+
+	// an unknown format still falls back to ms
+	t.equal(parse('2h', 'bogus'), 7200000)
+
+	t.end()
+})
+
 t('unicode support', t => {
 	parse.unit['сек'] = parse.unit['s'] // ru seconds
 	t.equal(parse('5сек'), 5000)