TypeScript Lab: CSS Class Composer

LAB / EXPLORATION

TypeScript Lab: CSS Class Composer

Planned

LAB 029 — Data Transformation
Combine optional class names into one clean class string.

LAB TypeScript Lab: CSS Class Composer Preview coming soon

LAB 029

TypeScript Lab: CSS Class Composer

Concept

Rest parameters and array methods normalize many optional values into one result.

Concept

Rest parameters and array methods normalize many optional values into one result.

Objective & Explanation

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

Learning Target

Objective

Combine optional class names into one clean class string.

Explanation

Rest parameters and array methods normalize many optional values into one result.

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

Data Layer

No persistent data layer. Keep all demonstration values inside the standalone project.

Sandbox Source

src/generator/generate.ts → classes()

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.

function classes(...values: Array<string | null | undefined>): string {
  return values
    .flatMap(value => String(value ?? "").split(/\s+/))
    .filter(Boolean)
    .join(" ");
}

classes("project-icon", "blue", undefined, "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: combine optional class names into one clean class string.

Data: None