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# Second Level Domains
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Support for second-level domain (SLD) detection and extraction with comprehensive country-specific domain knowledge.
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## Capabilities
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### Second Level Domain Detection
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```javascript { .api }
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/**
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 * Check if domain has a known second-level domain
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 * @param domain - Domain to check
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 * @returns Boolean indicating SLD presence
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 */
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SecondLevelDomains.has(domain: string): boolean;
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/**
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 * Check if domain is a known second-level domain
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 * @param domain - Domain to check
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 * @returns Boolean indicating if domain is an SLD
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 */
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SecondLevelDomains.is(domain: string): boolean;
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/**
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 * Get second-level domain portion of domain
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 * @param domain - Domain to extract SLD from
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 * @returns SLD portion or null if none
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 */
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SecondLevelDomains.get(domain: string): string | null;
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/**
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 * Object containing SLD mappings by top-level domain
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 */
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SecondLevelDomains.list: object;
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/**
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 * Restore previous SecondLevelDomains variable
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 * @returns Previous SecondLevelDomains variable value
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 */
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SecondLevelDomains.noConflict(): any;
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```
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**Usage Examples:**
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```javascript
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// Import SecondLevelDomains module
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import SecondLevelDomains from 'urijs/src/SecondLevelDomains';
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// Check for second-level domains
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console.log(SecondLevelDomains.has('bbc.co.uk')); // true
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console.log(SecondLevelDomains.has('example.com')); // false
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// Check if domain is an SLD
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console.log(SecondLevelDomains.is('co.uk')); // true
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console.log(SecondLevelDomains.is('com')); // false
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// Extract SLD portion
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console.log(SecondLevelDomains.get('bbc.co.uk')); // 'co.uk'
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console.log(SecondLevelDomains.get('example.com')); // null
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// Various country examples
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console.log(SecondLevelDomains.get('site.com.au')); // 'com.au'
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console.log(SecondLevelDomains.get('blog.gov.uk')); // 'gov.uk'
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console.log(SecondLevelDomains.get('shop.co.jp')); // 'co.jp'
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// Use with URI.js for domain parsing
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const uri = new URI('http://www.bbc.co.uk/news');
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console.log(uri.hostname()); // 'www.bbc.co.uk'
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console.log(uri.domain()); // 'bbc' (excludes SLD)
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console.log(uri.tld()); // 'co.uk' (includes SLD)
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console.log(uri.is('sld')); // true
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// Access SLD list directly
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console.log(SecondLevelDomains.list.uk); // ['co', 'gov', 'ac', ...]
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console.log(SecondLevelDomains.list.au); // ['com', 'gov', 'edu', ...]
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```