Do not mutate options (#67)

sindresorhus · Jan 18, 2024 · 2f55b19 · 2f55b19
1 parent 228dd07
commit 2f55b19
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Showing 2 changed files with 14 additions and 1 deletion.
diff --git a/index.js b/index.js
@@ -5,11 +5,13 @@ const pluralize = (word, count) => (count === 1 || count === 1n) ? word : `${wor
 
 const SECOND_ROUNDING_EPSILON = 0.000_000_1;
 
-export default function prettyMilliseconds(milliseconds, options = {}) {
+export default function prettyMilliseconds(milliseconds, options) {
 	if (!Number.isFinite(milliseconds)) {
 		throw new TypeError('Expected a finite number');
 	}
 
+	options = {...options};
+
 	if (options.colonNotation) {
 		options.compact = false;
 		options.formatSubMilliseconds = false;

diff --git a/test.js b/test.js
@@ -308,3 +308,14 @@ test('`colonNotation` option', t => {
 	t.is(format(Number.MAX_SAFE_INTEGER), '285616:151:08:59:00.9');
 	t.is(format(Number.MAX_VALUE), '5700447535712568547083700427941645003808085225292279557374304680873482979681895890593452082909683139015032646149857723394516742095667500822861020052921074432454921864096959420926519725467567456931340929884912090099277441972878147362726992943838905852030073647982034630974035871792165820638724934142:218:08:08:48');
 });
+
+test('pure', t => {
+	const runTest = options => {
+		const copy = {...options};
+		prettyMilliseconds(1, options);
+		t.deepEqual(options, copy);
+	};
+
+	runTest({colonNotation: true});
+	runTest({compact: true});
+});