Validation

import {
  isEmpty, isBlank, isString, isAlpha,
  isNumeric, isAlphaNumeric, isUpperCase, isLowerCase,
} from '@ppabari/strio/str';

These predicates never throw. Except for isString, they accept unknown and return false for non-string input.

isString

isString(value: unknown): value is string

isString('a'); // → true
isString(42);  // → false

isEmpty

isEmpty(value: unknown): boolean

true for zero-length strings (and non-strings).

isEmpty('');   // → true
isEmpty(' ');  // → false
isEmpty(null); // → true

isBlank

isBlank(value: unknown): boolean

true for empty or whitespace-only strings.

isBlank('   '); // → true
isBlank('a');   // → false

isAlpha

isAlpha(value: unknown): boolean

Only ASCII letters, non-empty.

isAlpha('Hello'); // → true
isAlpha('Hi5');   // → false

isNumeric

isNumeric(value: unknown): boolean

Only ASCII digits, non-empty. Checks the character class, not numeric parseability — '007' is numeric, '-1' and '1.5' are not.

isNumeric('12345'); // → true
isNumeric('1.5');   // → false

isAlphaNumeric

isAlphaNumeric(value: unknown): boolean

Only ASCII letters and digits, non-empty.

isAlphaNumeric('abc123'); // → true
isAlphaNumeric('abc 12'); // → false

isUpperCase / isLowerCase

isUpperCase(value: unknown): boolean
isLowerCase(value: unknown): boolean

Must contain at least one cased letter and be unchanged by toUpperCase() / toLowerCase().

isUpperCase('HELLO'); // → true
isUpperCase('Hello'); // → false
isUpperCase('123');   // → false (no cased letters)
isLowerCase('hello'); // → true