fix: match the format argument like an input unit

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

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))
 }

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)