TypeScript Lab: Expandable Parent State

LAB / EXPLORATION

TypeScript Lab: Expandable Parent State

Planned

LAB 061 — Browser State
Show expanded parent IDs inside a Set.

LAB TypeScript Lab: Expandable Parent State Preview coming soon

LAB 061

TypeScript Lab: Expandable Parent State

Concept

Set stores unique state values and supports fast membership checks.

Concept

Set stores unique state values and supports fast membership checks.

Objective & Explanation

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

Learning Target

Objective

Show expanded parent IDs inside a Set.

Explanation

Set stores unique state values and supports fast membership checks.

Project Plan

Structure, technologies, data boundary, and source connection.

Structure

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

Technologies

TypeScript
DOM
HTML
CSS
JSON

Data Layer

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

Sandbox Source

src/local-editor/client.ts → expandedParents

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 expandedParents = new Set<string>();

function toggleParent(id: string): void {
  expandedParents.has(id)
    ? expandedParents.delete(id)
    : expandedParents.add(id);
}

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 expanded parent IDs inside a Set.

Data: JSON