gistfile1.txt

# Prime Number API - Node.js (Express)

## Files:

### package.json


```json
{
  "name": "prime-api",
  "version": "1.0.0",
  "description": "Simple API to check if a number is prime",
  "main": "index.js",
  "scripts": {
    "start": "node index.js"
  },
  "dependencies": {
    "express": "^4.18.2"
  }
}
```

### index.js


```javascript
const express = require('express');
const app = express();
const port = 3000;

function isPrime(n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 === 0 || n % 3 === 0) return false;
  for (let i = 5; i * i <= n; i += 6) {
    if (n % i === 0 || n % (i + 2) === 0) return false;
  }
  return true;
}

app.get('/isprime', (req, res) => {
  const numberParam = req.query.number;
  if (!numberParam) {
    return res.status(400).json({ status: 'error', message: "Missing 'number' query parameter" });
  }
  const number = parseInt(numberParam, 10);
  if (isNaN(number)) {
    return res.status(400).json({ status: 'error', message: "'number' must be an integer" });
  }
  const result = isPrime(number);
  const message = result ? `${number} is a prime number` : `${number} is not a prime number`;
  res.json({ status: 'success', message });
});

app.listen(port, () => {
  console.log(`Prime API listening at http://localhost:${port}`);
});
```

### README.md


```markdown
# Prime Number API - Node.js (Express)

## Overview
This is a simple Node.js API built using the Express framework. It exposes one endpoint `/isprime` that takes a number as a query parameter and returns whether the number is prime or not.

## Prerequisites
- Node.js and npm installed

## Setup and Running

1. Install dependencies:

```bash
npm install
```

2. Run the API server:

```bash
npm start
```

The server will start on port 3000.

## Testing the API

You can test the API using curl or a browser.

Example using curl:

```bash
curl "http://localhost:3000/isprime?number=17"
```

Expected response:

```json
{
  "status": "success",
  "message": "17 is a prime number"
}
```

Example with invalid input:

```bash
curl "http://localhost:3000/isprime?number=abc"
```

Expected response:

```json
{
  "status": "error",
  "message": "'number' must be an integer"
}
```

## Notes

- The API expects the `number` query parameter to be an integer.
- Numbers less than 2 are considered not prime.
- Basic error handling is implemented for missing or invalid parameters.