TypeScript Lab: Generic API Client

LAB / EXPLORATION

TypeScript Lab: Generic API Client

Planned

LAB 087 — Node HTTP & APIs
Fetch typed JSON and display success or server errors.

LAB TypeScript Lab: Generic API Client Preview coming soon

LAB 087

TypeScript Lab: Generic API Client

Concept

A generic async function can return caller-selected response types.

Concept

A generic async function can return caller-selected response types.

Objective & Explanation

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

Learning Target

Objective

Fetch typed JSON and display success or server errors.

Explanation

A generic async function can return caller-selected response types.

Project Plan

Structure, technologies, data boundary, and source connection.

Structure

project/
├── package.json
├── tsconfig.json
├── public/
│   ├── index.html
│   └── styles.css
└── src/
    └── server.ts

Technologies

TypeScript
Node.js
HTTP
HTML
CSS

Data Layer

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

Sandbox Source

src/local-editor/client.ts → api<T>()

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

Use the interface to trigger and inspect the request/response behavior.

Code & Configuration

Starter configuration plus the focused implementation example.

Focused TypeScript

Implement this behavior first, then alter the input.

async function api<T>(url: string, options?: RequestInit): Promise<T> {
  const response = await fetch(url, options);

  if (!response.ok) {
    throw new Error(`${response.status} ${response.statusText}`);
  }

  return await response.json() as T;
}

Starter Configuration

Keep the project independently buildable.

package.json

{
  "type": "module",
  "scripts": {
    "build": "tsc",
    "start": "npm run build && node --enable-source-maps dist/server.js"
  },
  "devDependencies": {
    "@types/node": "^26.4.0",
    "typescript": "^7.0.2"
  }
}

tsconfig.json

{
  "compilerOptions": {
    "rootDir": "./src",
    "outDir": "./dist",
    "target": "ES2022",
    "module": "ES2022",
    "lib": ["ES2022", "DOM"],
    "types": ["node"],
    "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: fetch typed JSON and display success or server errors.

Data: None