How to fix RangeError: Compression level must be between -1 and 9 in Node.js

const zlib = require('zlib');

// Wrong - value outside valid range
const gzip = zlib.createGzip({ level: 10 }); // RangeError

// Correct - valid compression levels
const gzip1 = zlib.createGzip({ level: -1 }); // Default
const gzip2 = zlib.createGzip({ level: 0 });  // No compression
const gzip3 = zlib.createGzip({ level: 6 });  // Balanced
const gzip4 = zlib.createGzip({ level: 9 });  // Maximum compression

const zlib = require('zlib');

// Wrong - environment variable is a string
const level = process.env.COMPRESSION_LEVEL; // "9" (string)
const gzip = zlib.createGzip({ level }); // May cause error

// Correct - parse and validate
const level = parseInt(process.env.COMPRESSION_LEVEL || '-1', 10);

if (level < -1 || level > 9) {
  throw new Error('Invalid compression level. Must be between -1 and 9.');
}

const gzip = zlib.createGzip({ level });

const zlib = require('zlib');

// Wrong - passing level directly as second argument
const gzip = zlib.createGzip(level); // Incorrect syntax

// Correct - level is a property in options object
const gzip = zlib.createGzip({ level: 6 });

// For compression middleware
const compression = require('compression');
app.use(compression({
  level: 6,
  threshold: 0
}));

function createCompression(userLevel) {
  // Ensure level is a number
  const level = Number(userLevel);

  // Check if it's a valid number
  if (isNaN(level)) {
    throw new Error('Compression level must be a number');
  }

  // Ensure it's an integer in valid range
  const validLevel = Math.max(-1, Math.min(9, Math.floor(level)));

  return zlib.createGzip({ level: validLevel });
}

// Alternative: use a whitelist
const VALID_LEVELS = [-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9];

function createCompressionSafe(level) {
  if (!VALID_LEVELS.includes(level)) {
    throw new Error(`Invalid compression level: ${level}. Must be between -1 and 9.`);
  }

  return zlib.createGzip({ level });
}