You are given a positive integer num consisting only of digits 6 and 9. Return the maximum number you can get by changing at most one digit (6 becomes 9, and 9 becomes 6).

maximum69Number.js

/**
 * @param {number} num
 * @return {number}
 */
var maximum69Number  = function(num) {
    // Convert the number into an array of digits
    const digits = num.toString().split('');

    let maxNum = num;

    // Try flipping each digit one by one
    for (let i = 0; i < digits.length; i++) {
        // Clone the original digits array
        const tempDigits = [...digits];

        // Flip the current digit if it's 6 or 9
        if (tempDigits[i] === '6') {
            tempDigits[i] = '9';
        } else if (tempDigits[i] === '9') {
            tempDigits[i] = '6';
        }

        // Convert back to number and compare
        const newNum = parseInt(tempDigits.join(''), 10);
        maxNum = Math.max(maxNum, newNum);
    }

    return maxNum;
};