Upper Method

The upper() method transforms all strings in the collection to uppercase. This method is only available on collections of strings and returns a new collection with the transformed values.

Basic Syntax

upper(this: CollectionOperations<string>): CollectionOperations<string>

Examples

Basic Usage

import { collect } from 'ts-collect'

const words = collect(['hello', 'world', 'typescript'])
const uppercase = words.upper()

console.log(uppercase.all())
// ['HELLO', 'WORLD', 'TYPESCRIPT']

Working with Mixed Case

const codes = collect(['prod-123', 'dev-456', 'test-789'])
const normalized = codes.upper()

console.log(normalized.join(', '))
// "PROD-123, DEV-456, TEST-789"

Real-world Example: E-commerce Status Codes

class OrderStatusManager {
  private statuses: Collection<string>

  constructor(statusCodes: string[]) {
    this.statuses = collect(statusCodes)
  }

  normalizeStatusCodes(): Collection<string> {
    return this.statuses
      .map(status => status.trim())
      .filter(status => status.length > 0)
      .upper()
  }

  generateStatusLog(orderId: string): string {
    return this.normalizeStatusCodes()
      .map(status => `${orderId}:${status}`)
      .join('\n')
  }

  getDisplayStatuses(): string[] {
    return this.normalizeStatusCodes()
      .map(status => `Status: ${status}`)
      .toArray()
  }
}

// Usage
const orderManager = new OrderStatusManager([
  'pending',
  'in-transit',
  'delivered'
])

console.log(orderManager.normalizeStatusCodes().all())
// ['PENDING', 'IN-TRANSIT', 'DELIVERED']

console.log(orderManager.generateStatusLog('ORD-123'))
// ORD-123:PENDING
// ORD-123:IN-TRANSIT
// ORD-123:DELIVERED

Type Safety

// Only works with string collections
const strings = collect(['hello', 'world'])
const uppercased: Collection<string> = strings.upper() // ✓ Valid

// Won't work with number collections
const numbers = collect([1, 2, 3])
// numbers.upper() // ✗ TypeScript error

// Type preservation
type StringCollection = CollectionOperations<string>
const result: StringCollection = strings.upper() // ✓ Valid

Return Value

• Returns a new Collection<string> with uppercase values
• Original collection remains unchanged
• Maintains the order of elements
• Preserves collection chain methods
• Empty strings remain empty
• Non-string collections not supported

Common Use Cases

1. Status Codes

• Order statuses
• System codes
• Error codes
• Response types
• Process states

2. Data Standardization

• Reference codes
• Serial numbers
• Product SKUs
• Transaction IDs
• Category codes

3. System Integration

• API response codes
• Integration keys
• System identifiers
• Protocol messages
• Command strings

4. Display Formatting

• Headers
• Labels
• Alerts
• Notifications
• Emphasis text

5. Data Processing

• Log entries
• Audit trails
• System messages
• Debug output
• Event codes