TypeScript Lab: Primary Category Picker

LAB / EXPLORATION

TypeScript Lab: Primary Category Picker

Planned

LAB 035 — Data Transformation
Choose one visual category from several related categories.

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LAB 035

TypeScript Lab: Primary Category Picker

Concept

Ordered related data can produce one primary grouping value.

Concept

Ordered related data can produce one primary grouping value.

Objective & Explanation

What the project should make visible and why the concept matters.

Learning Target

Objective

Choose one visual category from several related categories.

Explanation

Ordered related data can produce one primary grouping value.

Project Plan

Structure, technologies, data boundary, and source connection.

Structure

project/
├── package.json
├── tsconfig.json
├── index.html
├── styles.css
└── src/
    └── app.ts

Technologies

TypeScript
HTML
CSS
JSON

Data Layer

Use a small local object, array, or JSON fixture so the transformation stays visible.

Sandbox Source

src/generator/generate.ts → primaryCategoryForRecord()

Build Instructions

Build only the focused behavior, then use the visual layer to inspect it.

Setup

Create the standalone project folder and listed files.

Implement

Implement the smallest version that demonstrates the concept.

Run & Inspect

Change one input and observe the visible output change.

Code & Configuration

Starter configuration plus the focused implementation example.

Focused TypeScript

Implement this behavior first, then alter the input.

type Category = { name: string; sortOrder: number };

function primaryCategory(categories: Category[]): Category | null {
  return [...categories]
    .sort((a, b) => a.sortOrder - b.sortOrder)[0] ?? null;
}

Starter Configuration

Keep the project independently buildable.

package.json

{
  "type": "module",
  "scripts": { "build": "tsc" },
  "devDependencies": { "typescript": "^7.0.2" }
}

tsconfig.json

{
  "compilerOptions": {
    "rootDir": "./src",
    "outDir": "./dist",
    "target": "ES2022",
    "module": "ES2022",
    "lib": ["ES2022", "DOM"],
    "strict": true,
    "sourceMap": true
  },
  "include": ["src/**/*.ts"]
}

Expected Visual Result

The output is the proof that the concept is working.

Visible Proof

The browser should visibly demonstrate: choose one visual category from several related categories.

Data: JSON