isAlpha

1/**
2 * Checks if a string contains only alphabetic characters (A–Z, a–z).
3 *
4 * @param str - The string to validate.
5 * @returns True if the string contains only letters, false otherwise.
6 */
7export function isAlpha(str: string): boolean {
8  return /^[A-Za-z]+$/.test(str);
9}

• Simple and Efficient Validation

  Uses a concise regular expression to quickly determine if a string contains only alphabetic characters.

• Language-Agnostic for Basic Latin Alphabet

  Focuses on ASCII A–Z and a–z, making it reliable for English-based validations.

• Zero Dependencies

  No need for external libraries or Unicode tables — lightweight and self-contained.

Tests | Examples

1test('isAlpha - valid alphabetic strings', () => {
2  expect(isAlpha('Hello')).toBe(true);
3  expect(isAlpha('world')).toBe(true);
4  expect(isAlpha('ABC')).toBe(true);
5});
6
7test('isAlpha - invalid strings with numbers', () => {
8  expect(isAlpha('Hello123')).toBe(false);
9  expect(isAlpha('123')).toBe(false);
10});
11
12test('isAlpha - invalid strings with symbols or spaces', () => {
13  expect(isAlpha('Hello!')).toBe(false);
14  expect(isAlpha('')).toBe(false);
15  expect(isAlpha('Hello World')).toBe(false);
16});

Common Use Cases

• First/Last Name Validation

  Ensure user input fields for names do not include numbers or special characters.

• Sanitizing Form Data

  Validate input fields where only letters are expected, such as country codes or tags.

• Token or Identifier Checks

  Confirm that specific identifiers or codes follow an alphabetic-only format.

• Basic Word Filtering

  Use in simple content moderation or spam detection to check for alphabet-only strings.