13 lines
530 B
TypeScript
13 lines
530 B
TypeScript
/**
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* Whether a normalized URL hostname names the local loopback authority.
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* @param hostname - WHATWG URL hostname (IPv6 literals retain brackets).
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* @returns true for localhost, IPv6 loopback, or any IPv4 address in 127/8.
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*/
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export function isLoopbackHostname(hostname: string): boolean {
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if (hostname === 'localhost' || hostname === '[::1]') return true
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const parts = hostname.split('.')
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return parts.length === 4
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&& parts[0] === '127'
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&& parts.every(part => /^\d{1,3}$/.test(part) && Number(part) <= 255)
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}
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