BW DatePicker Course — Complete Outline

What You'll Learn

Skills You'll Walk Away With

Not just syntax — the architectural thinking that makes the difference.

🏗️

Component Architecture

Structure & Organization

🔄

State Management

Observable & Reactive

📡

Event Systems

Pub/Sub & Delegation

🎨

Render Pipeline

DOM & Slots

🔌

Plugin Architecture

Extensibility

🚀

Production Build

Bundle & Publish

Code Progression

5 Versions — Your Journey

Each version builds on the previous. Clear progression from mess to mastery.

0

v0-naive

Naive Implementation

Everything in one file. It works, but it's messy. We'll critique this together.

1

v1-separated

Separated Core

StateManager + EventBus extracted. Single source of truth established.

2

v2-render

Render System

CalendarView + SlotManager + date-utils. Persistent DOM architecture.

3

v3-pipeline

Pipeline + Plugins

Render hooks. Facade pattern. Plugin system. Professional extensible API.

✓

v4-production

Production Ready

Rollup build. JavaScript types. npm publish. Ship it to the world!

Design Patterns

7 Patterns You'll Master

The patterns that separate junior developers from senior engineers.

🎭

Facade Pattern

BWDatePickerCore.js

Hide complexity behind a clean public API.

📡

Observer Pattern

StateManager.js

Auto-notify when state changes.

📢

Pub/Sub Pattern

EventBus.js

Decoupled component communication.

🧩

Slots Pattern

SlotManager.js

Customizable templates. Override any part of the UI.

🔄

Pipeline Pattern

Render Hooks

Interceptable render stages. Modify data before display.

🔌

Plugin Architecture

PluginSystem.js

Extend functionality. Import and use plugins.

🎯

Event Delegation

CalendarView.js

Single listener handles all clicks. Works after re-renders.

Core Files

7 Files We'll Build Together

Each file has one job. Together, they form the complete architecture.

🎭

BWDatePickerCore.js

Public API wrapper. Clean interface. Hides internal complexity from users.

Facade Chaining return this

📡

EventBus.js

Publish-subscribe event system. Components communicate without knowing each other.

Pub/Sub emit() on()

💾

StateManager.js

Observable state container. Single source of truth with auto-notify on changes.

Observer setState() get()

📅

CalendarView.js

Render logic for calendar grid. Hooks system for intercepting renders.

render() Hooks

🧩

SlotManager.js

Customizable templates. Users can override any part of the UI.

Slots Templates

🧮

date-utils.js

Date calculations. The algorithm behind generating 6×7 calendar grids.

Algorithm 6×7 Grid

🔌

PluginSystem.js

Manage installed plugins. Track active plugins, handle cleanup on destroy.

use() Extensibility

The Big Picture

Final Architecture

What you'll build by the end of this course.

📐 Architecture Diagram

                      USER CODE
                          │
      const picker = new BWDatePicker('#input').use(Plugin);
                          │
                          ▼
          ┌─────────────────────────────────────┐
          │        BWDatePickerCore             │
          │        Facade / Public API          │
          │                                     │
          │     open()  setDate()  on()  use()  │
          └─────────────────┬───────────────────┘
                            │
                            ▼
          ┌─────────────────────────────────────┐
          │           Controller                │
          │           Orchestrator              │
          │                                     │
          │    ┌──────────┐  ┌─────────────┐    │
          │    │ EventBus │  │ StateManager│    │
          │    └──────────┘  └─────────────┘    │
          │                                     │
          │    ┌──────────────┐  ┌──────────┐   │
          │    │ CalendarView │  │SlotManager│  │
          │    └──────────────┘  └──────────┘   │
          └─────────────────┬───────────────────┘
                            │
                            ▼
          ┌─────────────────────────────────────┐
          │          PluginSystem               │
          │          Extensions                 │
          └─────────────────────────────────────┘

Full Curriculum

5 Modules, 16 Episodes

From naive code to published npm package — the complete journey.

01

The Problem

3 Episodes • Why architecture matters

v0-naive

01

Why Build From Scratch?

The dependency problem. Black box libraries you can't debug. What we'll build.

Motivation Course Overview

~15 min

No code

02

The Beginner's DatePicker

Build a working datepicker the "wrong" way. Everything in one file. It works!

Live Coding datepicker.js

~25 min

v0 complete

03

Code Review — Everything Wrong

Mixed concerns, tight coupling, no extensibility, memory leaks. Let's fix it.

Code Review Anti-patterns

~20 min

Problem clear

02

Core Architecture

4 Episodes • Foundational patterns

v1-separated

04

Separation of Concerns

One class = one job. Introduce the target architecture we'll build toward.

SOLID Architecture

~20 min

Diagram

05

State Management

Single source of truth. Observable state with auto-notify. No magic.

Observer Pattern StateManager.js

~30 min

StateManager

06

Event System (Pub/Sub)

Publish-subscribe pattern. Decoupled communication. Fire and forget.

Pub/Sub Pattern EventBus.js

~25 min

EventBus

07

EventBus vs StateManager

When to use which. Events = "something happened." State = "something is."

Comparison Integration

~25 min

v1 complete

03

Render System

3 Episodes • DOM & Algorithm

v2-render

08

The Calendar Algorithm

generateMonthGrid() explained. 6×7 grid. Previous/next month days. Date utilities.

Algorithm date-utils.js

~14 min

date-utils

09

CalendarView & Rendering

renderDays() logic. isToday, isSelected, isWeekend. Building CSS classes from state.

Render Logic CalendarView.js

~15 min

CalendarView

10

SlotManager — Customizable Templates

Slots pattern. Default templates users can override. Separation of data and presentation.

Slots Pattern SlotManager.js

~14 min

v2 complete

04

Pipeline & Plugins

3 Episodes • Extensible Architecture

v3-pipeline

11

The Render Pipeline

Hooks: beforeRender, afterRender, beforeDayRender. How to intercept and modify data.

Pipeline Pattern Render Hooks

~14 min

Hooks System

12

Facade Pattern

BWDatePickerCore as public API. Hide complexity. return this for method chaining.

Facade Pattern BWDatePickerCore.js

~15 min

Public API

13

Plugin System

Plugins as functions. Context object. Built-in plugins: disableWeekends, holidays, minMax.

Plugin Architecture Extensibility

~16 min

v3 complete

05

Production

3 Episodes • Ship it

v4-production

14

Build System

Rollup setup. ESM, CJS, UMD formats. Minification. Each plugin = separate file.

Rollup Bundling UMD

~16 min

dist/

15

JavaScript Types

Declaration files (.d.ts). Type-safe events. Generic methods. No JavaScript required.

JavaScript index.d.ts

~14 min

types/

16

Publish to npm

package.json anatomy. npm publish workflow. Semantic versioning. README. Ship it!

npm Publishing Versioning

~15 min

Published! 🎉

Transformation

Your Journey

🍝

Spaghetti

One messy file

🧩

Separated

State & Events

🎨

Render

Slots & Views

🔌

Plugins

Extensible

🚀

Shipped

npm ready