JS Practice — Built-in Objects

Type Guard — validate schema

📖 Usage Example

function isUserSchema(x: unknown): x is { name: string; age: number } {
  return (
    typeof x === 'object' && x !== null &&
    typeof (x as any).name === 'string' &&
    typeof (x as any).age === 'number'
  )
}

Combining property checks into one type guard validates a complete object schema at runtime.

Type Guards: Schema Validation

Challenge: Implement validateUser(x: unknown): x is { name: string; age: number } — checking all required fields and their types.

validateUser({ name: 'Alice', age: 30 })    // → true
validateUser({ name: 'Bob' })               // → false (missing age)
validateUser({ name: 'Carol', age: 'old' }) // → false (wrong type)

💡 Hints (1)

• Check typeof for each property after verifying the key exists.