From 048039d3b8f47d24fa1b3957db29fa374869d6bf Mon Sep 17 00:00:00 2001
From: Mahmoud Hamdi <hmdy7486@gmail.com>
Date: Mon, 30 Mar 2026 00:42:12 +0200
Subject: [PATCH] fix: support scientific notation in parse() for roundtrip
 consistency
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format() produces scientific notation for very large millisecond values
(e.g., `ms(Number.MAX_SAFE_INTEGER)` → `"285616y"`), and for even larger
values JavaScript's number-to-string coercion uses exponential notation
(e.g., `"5.7e+297y"`). The parse() regex did not accept the `e` notation,
causing it to return NaN for format()'s own output.

Update the regex number pattern from `-?\d*\.?\d+` to
`-?\d*\.?\d+(?:e[+-]?\d+)?` so that parseFloat-compatible scientific
notation is matched correctly.

Fixes #284
---
 src/index.test.ts | 25 ++++++++++++++++++++++++-
 src/index.ts      |  2 +-
 src/parse.test.ts | 23 ++++++++++++++++++++++-
 3 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/src/index.test.ts b/src/index.test.ts
index 5035ab9..4d27c42 100644
--- a/src/index.test.ts
+++ b/src/index.test.ts
@@ -1,5 +1,5 @@
 import { describe, expect, it } from '@jest/globals';
-import { ms } from './index';
+import { ms, type StringValue } from './index';
 
 describe('ms(string)', () => {
   it('should not throw an error', () => {
@@ -329,6 +329,29 @@ describe('ms(number)', () => {
   });
 });
 
+// roundtrip
+
+describe('ms(roundtrip)', () => {
+  it('should roundtrip for common values', () => {
+    expect(ms(ms('1s'))).toBe('1s');
+    expect(ms(ms('1m'))).toBe('1m');
+    expect(ms(ms('1h'))).toBe('1h');
+    expect(ms(ms('1d'))).toBe('1d');
+    expect(ms(ms('1w'))).toBe('1w');
+    expect(ms(ms('1y'))).toBe('1y');
+  });
+
+  it('should not return NaN for format() output with large numbers', () => {
+    const formatted = ms(Number.MAX_SAFE_INTEGER) as StringValue;
+    expect(Number.isNaN(ms(formatted))).toBe(false);
+  });
+
+  it('should not return NaN for format() output with large negative numbers', () => {
+    const formatted = ms(-Number.MAX_SAFE_INTEGER) as StringValue;
+    expect(Number.isNaN(ms(formatted))).toBe(false);
+  });
+});
+
 // invalid inputs
 
 describe('ms(invalid inputs)', () => {
diff --git a/src/index.ts b/src/index.ts
index d50e3c7..388705e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -75,7 +75,7 @@ export function parse(str: string): number {
     );
   }
   const match =
-    /^(?<value>-?\d*\.?\d+) *(?<unit>milliseconds?|msecs?|ms|seconds?|secs?|s|minutes?|mins?|m|hours?|hrs?|h|days?|d|weeks?|w|months?|mo|years?|yrs?|y)?$/i.exec(
+    /^(?<value>-?\d*\.?\d+(?:e[+-]?\d+)?) *(?<unit>milliseconds?|msecs?|ms|seconds?|secs?|s|minutes?|mins?|m|hours?|hrs?|h|days?|d|weeks?|w|months?|mo|years?|yrs?|y)?$/i.exec(
       str,
     );
 
diff --git a/src/parse.test.ts b/src/parse.test.ts
index 9182411..e53dfdc 100644
--- a/src/parse.test.ts
+++ b/src/parse.test.ts
@@ -1,5 +1,5 @@
 import { describe, expect, it } from '@jest/globals';
-import { parse } from './index';
+import { format, parse } from './index';
 
 describe('parse(string)', () => {
   it('should not throw an error', () => {
@@ -142,6 +142,27 @@ describe('parse(long string)', () => {
   });
 });
 
+// scientific notation
+
+describe('parse(scientific notation)', () => {
+  it('should handle scientific notation in number part', () => {
+    expect(parse('1e3ms')).toBe(1000);
+    expect(parse('1.5e2ms')).toBe(150);
+    expect(parse('1e+3ms')).toBe(1000);
+    expect(parse('1e-3ms')).toBe(0.001);
+  });
+
+  it('should handle format() output for very large values', () => {
+    const formatted = format(Number.MAX_SAFE_INTEGER);
+    expect(Number.isNaN(parse(formatted))).toBe(false);
+  });
+
+  it('should handle format() output for very small negative values', () => {
+    const formatted = format(-Number.MAX_SAFE_INTEGER);
+    expect(Number.isNaN(parse(formatted))).toBe(false);
+  });
+});
+
 // invalid inputs
 
 describe('parse(invalid inputs)', () => {