TypeScript Lab: Predicate Traffic Lights

LAB / EXPLORATION

TypeScript Lab: Predicate Traffic Lights

Planned

LAB 032 — Data Transformation
Show which classification rules accept one record.

LAB TypeScript Lab: Predicate Traffic Lights Preview coming soon

LAB 032

TypeScript Lab: Predicate Traffic Lights

Concept

Small boolean functions turn business rules into reusable yes-or-no predicates.

Concept

Small boolean functions turn business rules into reusable yes-or-no predicates.

Objective & Explanation

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

Learning Target

Objective

Show which classification rules accept one record.

Explanation

Small boolean functions turn business rules into reusable yes-or-no predicates.

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 → isGeneralProject(), isDisplayableEntry(), isFeaturedProject()

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.

const isRosettaStone = (record: { type: string }) =>
  record.type === "rosetta-stone";

const isFeatured = (record: { featured: boolean }) =>
  Boolean(record.featured);

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: show which classification rules accept one record.

Data: JSON