From 90cd0a0c02bd15735eb06c54fc5ec18982b67089 Mon Sep 17 00:00:00 2001
From: bengsfort <bengsfort@gmail.com>
Date: Wed, 12 Nov 2025 14:34:15 +0200
Subject: [PATCH 1/2] Add restrictDecimals() and formatDuration()
 implementations to new number formatting module

---
 lib/formatting/__tests__/numbers.test.ts | 40 ++++++++++++++++
 lib/formatting/numbers.ts                | 58 ++++++++++++++++++++++++
 2 files changed, 98 insertions(+)
 create mode 100644 lib/formatting/__tests__/numbers.test.ts
 create mode 100644 lib/formatting/numbers.ts

diff --git a/lib/formatting/__tests__/numbers.test.ts b/lib/formatting/__tests__/numbers.test.ts
new file mode 100644
index 0000000..7f0f160
--- /dev/null
+++ b/lib/formatting/__tests__/numbers.test.ts
@@ -0,0 +1,40 @@
+import { describe, it, expect } from 'vitest';
+
+import { restrictDecimals, formatDuration } from '../numbers.js';
+
+describe('formatting/numbers', () => {
+  describe('restrictDecimals()', () => {
+    it('should limit large floats to a specified number of places', () => {
+      // We are intentionally trying to test that it restricts the float properly,
+      // therefore the float warning rule is ignorable.
+
+      const randomFloat = 1.5233219472835921359;
+      expect(restrictDecimals(randomFloat, 2)).toEqual(1.52);
+      expect(restrictDecimals(randomFloat, 1)).toEqual(1.5);
+      expect(restrictDecimals(randomFloat, 0)).toEqual(1);
+    });
+
+    it('should remove trailing zeroes', () => {
+      const randomFloat = 3.040203;
+      expect(restrictDecimals(randomFloat, 4)).toEqual(3.0402);
+      expect(restrictDecimals(randomFloat, 3)).toEqual(3.04);
+      expect(restrictDecimals(randomFloat, 1)).toEqual(3);
+    });
+  });
+
+  describe('formatDuration()', () => {
+    it('should display the value in the most appropriate timescale', () => {
+      const microSecs = 0.095;
+      expect(formatDuration(microSecs)).toEqual('95μs');
+
+      const millisecs = 50;
+      expect(formatDuration(millisecs)).toEqual('50ms');
+
+      const seconds = 3000;
+      expect(formatDuration(seconds)).toEqual('3s');
+
+      const minutes = 65000;
+      expect(formatDuration(minutes)).toEqual('1m 5s');
+    });
+  });
+});
diff --git a/lib/formatting/numbers.ts b/lib/formatting/numbers.ts
new file mode 100644
index 0000000..7c2eb02
--- /dev/null
+++ b/lib/formatting/numbers.ts
@@ -0,0 +1,58 @@
+/**
+ * Restricts the given value to a certain number of decimal places, but does NOT
+ * force that number of places like `.toFixed()` does. Trailing 0's will be removed.
+ */
+export function restrictDecimals(value: number, maxDecimalPlaces: number): number {
+  if (maxDecimalPlaces < 0) return value;
+  // When 0, dont use .toFixed since it rounds
+  if (maxDecimalPlaces === 0) {
+    return Math.floor(value);
+  }
+
+  // Force to fixed -> Convert back to number to remove trailing 0's.
+  return Number(value.toFixed(maxDecimalPlaces));
+}
+
+/**
+ * Takes a given duration in milliseconds and formats it into a more readable
+ * string value suitable for logging or display.
+ *
+ * Determines what timescale to use in an opinionated fashion:
+ *
+ * - Below 0.1ms switches to microseconds for more readability.
+ * - Between 0.1ms - 999ms displays milliseconds.
+ * - Between 1s - 59s displays seconds.
+ * - Over 1m will display Xminutes Yseconds.
+ *
+ * The timescale choices try to enforce readability patterns that make it easier
+ * to visually understand how much time something takes. Large values that could
+ * be dislayed as a smaller value at a larger timescale are preferred, as they
+ * require less mental math to understand.
+ */
+export function formatDuration(durationMs: number): string {
+  // Show microseconds when below 0.1ms
+  if (0.1 > durationMs) {
+    return `${restrictDecimals(durationMs * 1000, 0).toString(10)}μs`;
+  }
+
+  // Show milliseconds when below 1s
+  if (1000 > durationMs) {
+    return `${restrictDecimals(durationMs, 2).toString(10)}ms`;
+  }
+
+  const totalSeconds = restrictDecimals(durationMs / 1000, 2);
+  // Handle just seconds
+  if (60 > totalSeconds) {
+    return `${totalSeconds.toString(10)}s`;
+  }
+
+  // Handle seconds/minutes handling
+  const minutes = Math.floor(totalSeconds / 60);
+  const seconds = totalSeconds % 60;
+
+  const formatted: string[] = [];
+  if (1 >= minutes) formatted.push(`${minutes.toString(10)}m`);
+  formatted.push(`${seconds.toString(10)}s`);
+
+  return formatted.join(' ');
+}

From 23ad2c9a3c8f91bc743fb2519f384ec7149eb4f6 Mon Sep 17 00:00:00 2001
From: bengsfort <bengsfort@gmail.com>
Date: Wed, 12 Nov 2025 14:36:47 +0200
Subject: [PATCH 2/2] Expose formatting modules via exports.

---
 .changeset/blue-snails-unite.md | 5 +++++
 package.json                    | 6 +++++-
 2 files changed, 10 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/blue-snails-unite.md

diff --git a/.changeset/blue-snails-unite.md b/.changeset/blue-snails-unite.md
new file mode 100644
index 0000000..1d5dbf2
--- /dev/null
+++ b/.changeset/blue-snails-unite.md
@@ -0,0 +1,5 @@
+---
+'@bengsfort/stdlib': minor
+---
+
+Add new formatting modules including formatDuration() and restrictDecimals() functions.
diff --git a/package.json b/package.json
index 546c83e..646b621 100644
--- a/package.json
+++ b/package.json
@@ -30,6 +30,10 @@
     "./logging/node/*": {
       "default": "./dist/logging/node/*.js",
       "types": "./dist/logging/node/*.d.ts"
+    },
+    "./formatting/*": {
+      "default": "./dist/formatting/*.js",
+      "types": "./dist/formatting/*.d.ts"
     }
   },
   "files": [
@@ -61,4 +65,4 @@
     "typescript": "^5.7.3",
     "vitest": "^3.0.6"
   }
-}
\ No newline at end of file
+}