Lower Method

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

Basic Syntax

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

Examples

Basic Usage

import { collect } from 'ts-collect'

const words = collect(['Hello', 'WORLD', 'JavaScript'])
const lowered = words.lower()

console.log(lowered.all())
// ['hello', 'world', 'javascript']

Working with Mixed Case

const tags = collect(['JavaScript', 'TypeScript', 'NODE.js'])
const normalized = tags.lower()

console.log(normalized.join(', '))
// "javascript, typescript, node.js"

Real-world Example: E-commerce Search Normalization

class SearchNormalizer {
  private keywords: Collection<string>

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

  normalizeSearchTerms(): Collection<string> {
    return this.keywords
      .map(term => term.trim())
      .filter(term => term.length > 0)
      .lower()
  }

  generateUrlKeywords(): string {
    return this.normalizeSearchTerms()
      .join('+')
  }

  generateMetaKeywords(): string {
    return this.normalizeSearchTerms()
      .join(', ')
  }
}

// Usage
const searcher = new SearchNormalizer([
  'Laptop',
  'GAMING',
  'Pro-Level',
  'HIGH Performance'
])

console.log(searcher.normalizeSearchTerms().all())
// ['laptop', 'gaming', 'pro-level', 'high performance']

console.log(searcher.generateUrlKeywords())
// 'laptop+gaming+pro-level+high+performance'

Type Safety

// Only works with string collections
const strings = collect(['Hello', 'World'])
const lowered: Collection<string> = strings.lower() // ✓ Valid

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

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

Return Value

• Returns a new Collection<string> with lowercase 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. Search Normalization

• Query normalization
• Keyword standardization
• Search term processing
• Filter preparation
• Tag matching

2. Data Standardization

• Email addresses
• Usernames
• Reference codes
• Category names
• Tag normalization

3. URL Generation

• Path segments
• Query parameters
• Slug generation
• Route matching
• Link normalization

4. Comparison Operations

• Case-insensitive matching
• String equality checks
• Data validation
• Pattern matching
• Filter operations

5. Data Cleaning

• Input normalization
• Text standardization
• Format consistency
• Data preparation
• Import processing