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Time Guards

isValidTime​

Type guard that checks if a value is a valid time string in "HH:MM" format.

Function Signature​

function isValidTime(value: unknown): value is Time;

Parameters​

  • value: The value to check (any type)

Returns​

true if the value is a valid 24-hour time string, false otherwise

Example Usage​

import { isValidTime } from 'nhb-toolbox';

console.log(isValidTime("14:30")); // true
console.log(isValidTime("25:00")); // false (invalid hour)
console.log(isValidTime("12:60")); // false (invalid minute)
console.log(isValidTime(1234));    // false (not a string)

Validation Rules​

  1. Must be a string in "HH:MM" format
  2. Hours must be between 00-23
  3. Minutes must be between 00-59
  4. Leading zeros required for single-digit values

Alias​

  • isValidTimeString

Type Definition​

type ClockTime = `${ClockHour}:${ClockMinute}`;
type ClockHour = '00'|'01'|...|'23';
type ClockMinute = '00'|'01'|...|'59';

isValidUTCOffSet​

Type guard that checks if a value is a valid UTC offset string.

Function Signature​

function isValidUTCOffSet(value: unknown): value is UTCOffSet;

Parameters​

  • value: The value to check (any type)

Returns​

true if the value is a valid UTC offset string, false otherwise

Example Usage​

import { isValidUTCOffSet } from 'nhb-toolbox';

console.log(isValidUTCOffSet("UTC+05:30")); // true
console.log(isValidUTCOffSet("UTC-14:00")); // true
console.log(isValidUTCOffSet("GMT+08:00")); // false (invalid prefix)
console.log(isValidUTCOffSet("UTC+25:00")); // false (invalid hour)

Validation Rules​

  1. Must start with "UTC" prefix
  2. Must be followed by + or - sign
  3. Hours must be 1-2 digits
  4. Must include colon separator
  5. Minutes must be exactly 2 digits
  6. Followed by valid time components (hours 00-14, minutes 00/15/30/45)

Alias​

  • isValidUTC

Type Definition​

type UTCOffSet = `UTC${PositiveUTCHour|NegativeUTCHour}:${UTCMinute}`;

Conclusion​

These type guards provide:

  1. Strict validation of time formats
  2. Type narrowing for TypeScript
  3. Consistent checking across applications
  4. Safety for time-related operations

Ideal for:

  • Input validation
  • API response checking
  • Type-safe time operations
  • Data sanitization