TypeScript Lab: Read POST JSON

LAB / EXPLORATION

Planned

LAB 085 — Node HTTP & APIs
Submit JSON and display what the server received.

LAB TypeScript Lab: Read POST JSON Preview coming soon

LAB 085

TypeScript Lab: Read POST JSON

Concept

Request bodies arrive as chunks that must be combined and parsed.

Concept

Request bodies arrive as chunks that must be combined and parsed.

Objective & Explanation

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

Learning Target

Objective

Submit JSON and display what the server received.

Explanation

Request bodies arrive as chunks that must be combined and parsed.

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/server.ts → readJson()

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 readJson(req: IncomingMessage): Promise<unknown> {
  const chunks: Buffer[] = [];

  for await (const chunk of req) {
    chunks.push(Buffer.from(chunk));
  }

  return JSON.parse(Buffer.concat(chunks).toString("utf8"));
}

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: submit JSON and display what the server received.

Data: None