f691258a5c
* refactor(agents): move prescriptive content from knowledge-base to rules - Create architecture-page-level-auth.md for Next.js auth checks - Create data-prefer-select-over-include.md for Prisma query optimization - Create performance-dayjs-usage.md for Day.js performance guidelines - Create quality-avoid-barrel-imports.md for import best practices - Update knowledge-base.md to reference rules directory - Remove duplicated prescriptive content from knowledge-base.md Co-Authored-By: eunjae@cal.com <hey@eunjae.dev> * chore(agents): remove redundant rules reference from knowledge-base Co-Authored-By: eunjae@cal.com <hey@eunjae.dev> * docs: add agents/rules reference to AGENTS.md extended documentation Co-Authored-By: eunjae@cal.com <hey@eunjae.dev> --------- Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
54 lines
1.7 KiB
Markdown
54 lines
1.7 KiB
Markdown
---
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title: Day.js Performance Guidelines
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impact: HIGH
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impactDescription: Significant performance improvement in date-heavy operations
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tags: performance, dates, dayjs
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---
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## Day.js Performance Guidelines
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**Impact: HIGH (Significant performance improvement in date-heavy operations)**
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Day.js with the `@calcom/dayjs` wrapper is heavy because it pre-loads all plugins including locale handling. Use alternatives when strict timezone awareness isn't required.
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**Incorrect (using Day.js unnecessarily):**
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```typescript
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// Slow in performance-critical code (loops)
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dates.map((date) => dayjs(date).add(1, "day").format());
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// Using Dayjs for simple date operations
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const startOfMonth = dayjs().startOf("month");
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```
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**Correct (using performant alternatives):**
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```typescript
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// Use .utc() for better performance when timezone doesn't matter
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dates.map((date) => dayjs.utc(date).add(1, "day").format());
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// Use native Date when possible
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dates.map((date) => new Date(date.valueOf() + 24 * 60 * 60 * 1000));
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// Use date-fns for simple operations
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import { startOfMonth, endOfDay } from "date-fns";
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const monthStart = startOfMonth(dateObj);
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const dayEnd = endOfDay(dateObj);
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// For browser locale, use Intl with i18n
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const { i18n: { language } } = useLocale();
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new Intl.DateTimeFormat(language).format(date);
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```
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**When to use Day.js:**
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- When you need strict timezone awareness (e.g., in the Booker)
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- When working with complex timezone conversions
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- When the performance impact is negligible (non-loop operations)
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**When to avoid Day.js:**
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- Simple date arithmetic
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- Date formatting without timezone concerns
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- Performance-critical loops over dates
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Reference: [Cal.com Engineering Standards](https://cal.com/blog/engineering-in-2026-and-beyond)
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