Turn a one digit number into a two digit number string.

to2digits.js

/**
 * Turn a one digit number into a two digit number string.
 *
 * If you can not garantee that the number n is a number, simply wrap it with Number(n) to turn the string into a number.
 *
 * The following three functions are doing the same thing. You can choose which one fits the best purpose for you. The last one has the most legacy support.
 */

/**
 * Turn a one digit number into a two digit number string by using the padStart method.
 *
 * @param {number} n An integer.
 *
 * @returns {string}
 */
function to2digits(n) {
    return String(n).padStart(2, '0');
}

/**
 * Turn a one digit number into a two digit number string.
 *
 * @param {number} n An integer.
 *
 * @returns {string}
 */
const to2digits = n => (n < 10 ? '0' + n : n);

/**
 * Turn a one digit number into a two digit number string.
 *
 * @param {number} n An integer.
 *
 * @returns {string}
 */
function to2digits(n) {
    return n < 10 ? '0' + n : n;
}

/**
 * Turn a one digit number into a two digit number string.
 *
 * @param {number} n An integer.
 *
 * @returns {string}
 */
function to2digits(n) {
    if (n < 10) {
        return '0' + n;
    }

    return n;
}