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// Simulating TypeScript's built-in conditional types
// In TypeScript, these would be:
// type Extract<T, U> = T extends U ? T : never;
// type Exclude<T, U> = T extends U ? never : T;

// Helper functions to demonstrate the concepts
function simulateExtract(items, typeToExtract) {
  // Extract types that match the condition
  return items.filter(item => typeof item === typeToExtract);
}

function simulateExclude(items, typeToExclude) {
  // Exclude types that match the condition
  return items.filter(item => typeof item !== typeToExclude);
}

function simulateNonNullable(items) {
  // Filter out null and undefined values
  return items.filter(item => item !== null && item !== undefined);
}

// Example data
const mixedData = ["hello", 42, true, null, undefined, "world"];

// Demonstrating Extract<T, U>
console.log("Extract<string | number | boolean, string>:");
console.log(simulateExtract(mixedData, "string")); // ["hello", "world"]

// Demonstrating Exclude<T, U>
console.log("Exclude<string | number | boolean, string>:");
console.log(simulateExclude(mixedData, "string")); // [42, true, null, undefined]

// Demonstrating NonNullable<T>
console.log("NonNullable<string | null | undefined>:");
console.log(simulateNonNullable(mixedData)); // ["hello", 42, true, "world"]

// For Parameters and ReturnType - simple demonstration
function exampleFunction(a, b) {
  return a + b;
}

console.log("Parameters of function (a, b) => a + b:");
console.log("In TypeScript: [string, number]");

console.log("ReturnType of () => string:");
console.log("In TypeScript: string");

Extract:
[ 'hello', 'world' ]
Exclude:
[ 42, true, null, undefined ]
NonNullable:
[ 'hello', 42, true, 'world' ]
Parameters of function (a, b) => a + b:
In TypeScript: [string, number]
ReturnType of () => string:
In TypeScript: string