solution.js

/**
 * @param {number} num
 * @return {string[]}
 */
var readBinaryWatch = function(num) {
    let preHoursMap = {
        0: ['0'],
        1: ['1', '2', '4', '8'],
        2: ['3', '5', '9', '6', '10'],
        3: ['7', '11']
    }
    let preMinsMap = {
        0: ['00'],
        1: ['01', '02', '04', '08', '16', '32'],
        2: ['03', '05', '09', '17', '33', '06', '10', '18', '34', '12', '20', '36', '24', '40', '48'],
        3: ['07', '11', '19', '35', '13', '21', '37', '25', '41', '49', '14', '22', '38', '26', '42', '50', '28', '44', '52', '56'],
        4: ['15', '23', '39', '27', '43', '51', '29', '45', '53', '57', '30', '46', '54', '58'],
        5: ['31', '47', '55', '59']
    }

    let res = []

    for (let i = 0; i < 4; i++) {
        if (preMinsMap[num - i]) {
            preHoursMap[i].forEach(hour => {
                preMinsMap[num - i].forEach(min => res.push(hour + ':' + min))
            })
        }
    }
        
    return res
};