From 317c7e67a3c44ce4a528228d42b92d9835a1bd49 Mon Sep 17 00:00:00 2001
From: wuyangfan <yangfan.wu@succaiss.com>
Date: Mon, 25 May 2026 15:38:02 +0800
Subject: [PATCH] fix(parse): support scientific notation for format()
 roundtrip

Extend the numeric capture group to accept exponent suffixes so
parse() can handle strings produced by format() for very large
values like Number.MAX_VALUE.

Fixes vercel/ms#284

Co-authored-by: Cursor <cursoragent@cursor.com>
---
 src/index.test.ts |  4 ++++
 src/index.ts      |  2 +-
 src/parse.test.ts | 16 +++++++++++++++-
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/index.test.ts b/src/index.test.ts
index 5035ab9..6b03629 100644
--- a/src/index.test.ts
+++ b/src/index.test.ts
@@ -327,6 +327,10 @@ describe('ms(number)', () => {
 
     expect(ms(-234234234)).toBe('-3d');
   });
+
+  it('should roundtrip very large values that format in scientific notation', () => {
+    expect(ms(ms(Number.MAX_VALUE))).toBe(Number.MAX_VALUE);
+  });
 });
 
 // invalid inputs
diff --git a/src/index.ts b/src/index.ts
index d50e3c7..0796c11 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..a8e8f1b 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', () => {
@@ -66,6 +66,20 @@ describe('parse(string)', () => {
     expect(parse('.5ms')).toBe(0.5);
   });
 
+  it('should parse scientific notation values', () => {
+    expect(parse('1e3ms')).toBe(1000);
+    expect(parse('1.5e2s')).toBe(150000);
+    expect(parse('-1e3ms')).toBe(-1000);
+    expect(parse('1E3ms')).toBe(1000);
+    expect(parse('1e+3ms')).toBe(1000);
+  });
+
+  it('should roundtrip format output with scientific notation', () => {
+    const formatted = format(Number.MAX_VALUE);
+    expect(formatted).toMatch(/e[+-]\d+y$/i);
+    expect(parse(formatted)).toBe(Number.MAX_VALUE);
+  });
+
   it('should work with negative integers', () => {
     expect(parse('-100ms')).toBe(-100);
   });