A Javascript program to convert a given number to its roman numeral representation

roman-numerals.js

/**
 * Write a program to encode a given number in roman numeral form
 // I - 1
 // V - 5
 // X - 10
 // L - 50
 // C - 100
 // D - 500
 // M - 1000
 * @param {*} number 
 * function encode(number) {
 *      return "XV";
 * }
 */
function encode(number) {
    let exponent = 0;
    let roman = "";
    while(number > 0) {
        let digit = number % 10;
        // console.log(encodeDigit(digit, exponent));
        roman = encodeDigit(digit, exponent)+roman;
        number = Math.floor(number / 10);
        exponent++;
    }
    // console.log(`The roman form of ${number} is ${roman}`);
    return roman;
}

const numerals = [
    {min: 'I', mid: 'V'},
    {min: 'X', mid: 'L'},
    {min: 'C', mid: 'D'},
    {min: 'M', mid: 'N'},
];
function encodeDigit(number, exponent) {
    const min = numerals[exponent].min;
    const mid = numerals[exponent].mid;
    switch(number) {
        case 0:
            return "";
        case 1:
            return min;
        case 2:
            return `${min}${min}`;
        case 3:
            return `${min}${min}${min}`;
        case 4:
            return `${min}${mid}`;
        case 5:
            return mid;
        case 6:
            return `${mid}${min}`;
        case 7:
            return `${mid}${min}${min}`;
        case 8:
            return `${mid}${min}${min}${min}`;
        case 9:
            return `${min}${numerals[exponent+1].min}`;
    }
}

function assert(expected, number) {
    const actual = encode(number);
    if (expected === actual) {
        console.log(`Passed ${number} === ${expected}`);
        return;
    }

    console.trace(`Expected ${expected} for ${number} but is actually ${actual}`);
}
function main() {
    assert("CCXLVII", 247);
    assert("CCXCVIII", 298);
    assert("M", 1000);
    assert("CM", 900);
    assert("LV", 55);
    assert("MMMCMXCIX", 3999);
}
main();