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appendZeroOneDigit

The appendZeroOneDigit function adds a leading zero to a single-digit number, converting it to a string. It handles both string and number inputs, ensuring the output is always a string.

Function Signature#

const appendZeroOneDigit = (num: string | number) => string;

Parameters#

num: string | number: The input value, which can be either a number or a string that represents a number.

Returns#

string:

  • If the number is a single-digit (0-9), the function returns a string with a leading zero (e.g., 07).

  • If the number is greater than or equal to 10, or negative, it returns the number as a string without modification.

Example Usage#

Example 1: Single-digit number#

const result = appendZeroOneDigit(7); console.log(result); // 출력: '07'

Example 2: Double-digit number#

const result = appendZeroOneDigit(12); console.log(result); // 출력: '12'

Example 3: String input with single-digit#

const result = appendZeroOneDigit('3'); console.log(result); // 출력: '03'

Example 4: String input with double-digit#

const result = appendZeroOneDigit('15'); console.log(result); // 출력: '15'

Example 5: Invalid input#

try { appendZeroOneDigit('abc'); } catch (e) { console.log(e.message); } // 출력: 'Invalid input: input should be a number or a string that can be converted to a number'

Explanation#

  1. Input Type Check: The function first checks if the input is a string. If so, it converts the string to an integer using parseInt.

  2. NaN Check: If the input cannot be converted to a valid number, an error is thrown with a descriptive message.

  3. Single-Digit Check: If the number is between 0 and 9 (inclusive), the function adds a leading zero and returns it as a string.

  4. Other Cases: For all other valid numbers, the function simply returns the number as a string